Pro tip for countries looking to keep their tourism numbers up: Don't annoy China.

That's the lesson South Korea is learning the hard way. The country suffered a 40% plunge in Chinese visitors last month, according to the Korea Tourism Organization.

Chinese tour groups have been canceling trips because of anger over the deployment of a controversial U.S.-built missile defense system in South Korea. Chinese authorities are believed to have told travel agencies last month to stop selling trips to South Korea.

The outlook is bleak, too. Bookings for stays of four to eight nights by Chinese visitors are down 28% in the second quarter of 2017 compared with a year earlier, according to ForwardKeys, a provider of data on the travel industry.

Related: South Korean company to China: Don't blame us for THAAD missiles

China has vigorously opposed the stationing of the THAAD anti-missile system in South Korea, complaining that it threatens security and fuels tensions in the region. The South Korean government says the system is designed to reduce the threat from North Korean missiles.

South Korean businesses that rely on foreign tourists are feeling the chill. Chinese citizens accounted for eight million of the roughly 17 million people who visited South Korea last year and are big spenders.

"There's been a big reduction in the number of groups of Chinese tourists in Seoul since the THAAD missile crisis," said Kil Ki-yon, the director of Seoul Tiger Bus, a company that takes Chinese visitors on tours of the city.

South Korean conglomerate Lotte said its duty free stores have taken a huge hit, too.

Sales to Chinese customers between mid-March and mid-April plunged 40% from a year earlier, according to a spokesman for the group. Chinese tourists tend to account for as much as 80% of duty free sales, he added.

The difficulties come at a time when outbound travel by China's burgeoning middle class is surging. The Chinese spent $261 billion traveling abroad last year, according to the World Tourism Organization, a 12% increase compared with the previous year.

ForwardKeys said Southeast Asian countries are the most likely to benefit from South Korea's problems with China.

Related: Parts of controversial US anti-missile system moved to South Korean site

The tensions between Beijing and Seoul over THAAD show little sign of easing. South Korea is pushing ahead with the system, parts of which have now arrived at the planned deployment site, the South Korean Defense Ministry said Wednesday.

In response, the Chinese Foreign Ministry reiterated its opposition, warning that "China will firmly take necessary measures to safeguard its own interests."

-- Sol Han, Hyunsoo Woo and Steven Jiang contributed to this report.</s>U.S. President Donald Trump said on Thursday a major conflict with North Korea is possible in the standoff over its nuclear and missile programs, but he would prefer a diplomatic outcome to the dispute.

"There is a chance that we could end up having a major, major conflict with North Korea. Absolutely," Trump told Reuters in an Oval Office interview ahead of his 100th day in office on Saturday.

Nonetheless, Trump said he wanted to peacefully resolve a crisis that has bedeviled multiple U.S. presidents, a path that he and his administration are emphasizing by preparing a variety of new economic sanctions while not taking the military option off the table.

"We'd love to solve things diplomatically but it's very difficult," he said.

In other highlights of the 42-minute interview, Trump was cool to speaking again with Taiwan's president after an earlier telephone call with her angered China.

He also said he wants South Korea to pay the cost of the U.S. THAAD anti-missile defense system, which he estimated at $1 billion, and intends to renegotiate or terminate a U.S. free trade pact with South Korea because of a deep trade deficit with Seoul.

Asked when he would announce his intention to renegotiate the pact, Trump said: “Very soon. I’m announcing it now.”

Trump also said he was considering adding stops to Israel and Saudi Arabia to a Europe trip next month, emphasizing that he wanted to see an Israeli-Palestinian peace. He complained that Saudi Arabia was not paying its fair share for U.S. defense.

Asked about the fight against Islamic State, Trump said the militant group had to be defeated.

"I have to say, there is an end. And it has to be humiliation," he said, when asked about what the endgame was for defeating Islamist violent extremism.

Trump said North Korea was his biggest global challenge. He lavished praise on Chinese President Xi Jinping for Chinese assistance in trying to rein in Pyongyang. The two leaders met in Florida earlier this month.

"I believe he is trying very hard. He certainly doesn’t want to see turmoil and death. He doesn’t want to see it. He is a good man. He is a very good man and I got to know him very well.

"With that being said, he loves China and he loves the people of China. I know he would like to be able to do something, perhaps it's possible that he can’t," Trump said.

Trump spoke just a day after he and his top national security advisers briefed U.S. lawmakers on the North Korean threat and one day before Secretary of State Rex Tillerson will press the United Nations Security Council on sanctions to further isolate Pyongyang over its nuclear and missile programs.

The Trump administration on Wednesday declared North Korea "an urgent national security threat and top foreign policy priority." It said it was focusing on economic and diplomatic pressure, including Chinese cooperation in containing its defiant neighbor and ally, and remained open to negotiations.

U.S. officials said military strikes remained an option but played down the prospect, though the administration has sent an aircraft carrier and a nuclear-powered submarine to the region in a show of force.

Any direct U.S. military action would run the risk of massive North Korean retaliation and huge casualties in Japan and South Korea and among U.S. forces in both countries.

Trump, asked if he considered North Korean leader Kim Jong Un to be rational, said he was operating from the assumption that he is rational. He noted that Kim had taken over his country at an early age.

"He's 27 years old. His father dies, took over a regime. So say what you want but that is not easy, especially at that age.

"I'm not giving him credit or not giving him credit, I'm just saying that's a very hard thing to do. As to whether or not he's rational, I have no opinion on it. I hope he's rational," he said.

Trump, sipping a Coke delivered by an aide after the president ordered it by pressing a button on his desk, rebuffed an overture from Taiwan President Tsai Ing-wen, who told Reuters a direct phone call with Trump could take place again after their first conversation in early December angered Beijing.

"My problem is that I have established a very good personal relationship with President Xi," said Trump. "I really feel that he is doing everything in his power to help us with a big situation. So I wouldn’t want to be causing difficulty right now for him.

"So I would certainly want to speak to him first."

Trump also said he hoped to avoid a potential government shutdown amid a dispute between congressional Republicans and Democrats over a spending deal with a Saturday deadline looming.

But he said if a shutdown takes place, it will be the Democrats' fault for trying to add money to the legislation to "bail out Puerto Rico" and other items.

He also defended the one-page tax plan he unveiled on Wednesday from criticism that it would increase the U.S. deficit, saying better trade deals and economic growth would offset the costs.

"We will do trade deals that are going to make up for a tremendous amount of the deficit. We are going to be doing trade deals that are going to be much better trade deals," Trump said.</s>SEOUL (Reuters) - U.S. President Donald Trump’s suggestion that Seoul pay for the THAAD advanced U.S. missile defense system would be an “impossible option,” a top foreign policy adviser to South Korean presidential frontrunner Moon Jae-in said on Friday.

FILE PHOTO - A Terminal High Altitude Area Defense (THAAD) interceptor is launched during a successful intercept test, in this undated handout photo provided by the U.S. Department of Defense, Missile Defense Agency. U.S. Department of Defense, Missile Defense Agency/Handout via Reuters/File Photo

Trump told Reuters in an interview on Thursday he wants South Korea to pay for the $1 billion Terminal High Altitude Area Defense (THAAD) system.

“Even if we purchase THAAD, its main operation would be in the hands of the United States,” said Kim Ki-jung, a foreign policy adviser to Moon and professor at Seoul’s Yonsei University.

“So purchasing it would be an impossible option. That was our topic when we were considering the options,” Kim said.

Moon is leading polls by a wide margin ahead of a May 9 election to replace impeached former President Park Geun-hye, whose government agreed last year to deploy THAAD.

Lee Ji-soo, a spokesman for Moon, said campaign officials were aware of the reported comments by Trump and deliberating his demand that South Korea pay for THAAD but added that there was no official comment from Moon’s camp yet.

Trump, in the interview as he prepared to mark 100 days in office on Saturday, also accused another ally, Saudi Arabia, of not paying enough for the U.S. defense umbrella.

Trump’s comments harked back to his populist campaign rhetoric and Bonnie Glaser, an Asia expert at Washington’s Center for Strategic and International Studies, said they betrayed a lack of strategic thinking.

“Trump’s remarks reflect his persistent desire for allies to pay more for their defense,” she said. “As far as their impact on South Korea’s election, they will likely boost support for Moon, and if he wins, it will make it harder for the U.S. to sustain a hardline policy against North Korea. So Trump’s remarks don’t seem very strategic to me.”

Trump’s comments provoked some consternation among Democrats and Republicans in the U.S. Congress.

Congressional aides noted the THAAD deployment came after years of discussions, in which South Korea took a great deal of convincing and then suffered economic retaliation from China.

“It just seems completely tone deaf ... That system isn’t just good for South Korea, it’s also good for us,” one aide said, adding that it would also defend U.S. troops in South Korea and deter North Korea from targeting U.S. territory.

The U.S. military started THAAD deployment in early March, despite strong opposition from China, which says the system’s radar can be used to spy into its territory. The deployment has also prompted a North Korean warning of retaliation.

South Korea said on Wednesday major elements of the system were moved into the planned site in Seonjgu in the south of the country and would be fully operational by the end of this year.

That system will have initial operational capability “very soon,” a Pentagon spokesman told reporters on Friday.

The Pentagon has called THAAD a “critical measure” to defend South Koreans and U.S. forces and the top U.S. commander in the Pacific, Admiral Harry Harris, said the system would be operational “in coming days.”

Seonjgu residents have protested, citing safety fears and its potential to be a wartime target.

The United States currently has six THAAD batteries worldwide and a former U.S. State Department official, who estimated the cost of each at about $1.2 billion, said Washington would not want to sell THAAD to Seoul.

“We want to retain THAAD in our arsenal, consistent with all other U.S. weapons systems deployed on the Korean peninsula. We own them. We retain them. We have the right to redeploy them,” the official said, speaking on condition of anonymity.</s>A U.S. missile defense system that's now being installed in South Korea will be operational "in the coming days," says Adm. Harry Harris, commander of the U.S. Pacific Command.

President Trump and Defense Secretary James Mattis have said all options are on the table to counter what Harris called "the reckless North Korean regime" in his testimony Wednesday before the House Armed Services Committee. But Harris also stated, "We want to bring Kim Jong Un to his senses, not to his knees."

Hours before the admiral spoke to members of Congress, parts of the Terminal High Altitude Area Defense missile system, or THAAD, began the trip to their deployment site in a rural part of South Korea.

"The overnight, unannounced operation came just six days after U.S. Forces Korea (USFK) secured the land in Seongju, North Gyeongsang Province, from the South Korean government," the Yonhap News Agency reports.

Large components of the U.S. THAAD system began landing in South Korea early last month, under an agreement that was reached last July.

Wednesday's convoy of trucks and equipment included some 20 trucks, the Korea Herald reports, adding, "Although covered by plastic boxes and wrapping, they were believed to include a radar, launchers, interceptors, a fire control and communications unit, a power generator and a cooler."

Harris testified ahead of an unusual meeting at the White House on Wednesday, when all 100 U.S. senators are expected to attend a classified briefing on North Korea.

China has opposed the deployment, saying the system's radar could provide a new way to spy on its military and that THAAD missiles could undercut China's nuclear deterrent. The country has also warned of an arms race between defensive and offensive weapons on the Korean Peninsula.

The U.S. says the THAAD system is not an offensive weapon — a point that Adm. Harris reiterated on Capitol Hill on Wednesday.

"This system is a defensive system that will help protect South Korea from ballistic missile attacks from North Korea," Harris told the House committee during Wednesday's public hearing. "It is a purely defensive system," he added, saying that the THAAD components are "aimed north" — not at China to the west.

Harris said that he takes Kim Jong Un at his word when he threatens U.S. targets. The leader has previously spoken of striking U.S. cities, and this week, North Korea threatened to sink the USS Carl Vinson aircraft carrier.

"I believe that we have to look at North Korea as if Kim Jong Un will do what he says," Harris told the panel, while acknowledging that for now, at least, there's a "capability gap" between what the North Korean leader has threatened and what his military could achieve.

But when that gap is closed, Harris also said, it would represent an "inflection point, and we're going to have to deal with that, I believe."

In South Korea, the deployment has stirred a mix of reactions, including protests and clashes with police Wednesday.

"South Korean television showed images of demonstrators in rural Seongju county, about 155 miles south of the capital, hurling water bottles at trucks carrying parts of the THAAD system," reporter Jason Strother tells NPR from Seoul. "Reports say protesters tried to block its delivery to a golf course that's being converted into a base."</s>A U.S. missile defense system that's now being installed in South Korea will be operational "in the coming days," says Adm. Harry Harris, commander of the U.S. Pacific Command.

President Trump and Defense Secretary James Mattis have said all options are on the table to counter what Harris called "the reckless North Korean regime" in his testimony Wednesday before the House Armed Services Committee. But Harris also stated, "We want to bring Kim Jong Un to his senses, not to his knees."

Hours before the admiral spoke to members of Congress, parts of the Terminal High Altitude Area Defense missile system, or THAAD, began the trip to their deployment site in a rural part of South Korea.

"The overnight, unannounced operation came just six days after U.S. Forces Korea (USFK) secured the land in Seongju, North Gyeongsang Province, from the South Korean government," the Yonhap News Agency reports.

Large components of the U.S. THAAD system began landing in South Korea early last month, under an agreement that was reached last July.

Wednesday's convoy of trucks and equipment included some 20 trucks, the Korea Herald reports, adding, "Although covered by plastic boxes and wrapping, they were believed to include a radar, launchers, interceptors, a fire control and communications unit, a power generator and a cooler."

Harris testified ahead of an unusual meeting at the White House on Wednesday, when all 100 U.S. senators are expected to attend a classified briefing on North Korea.

China has opposed the deployment, saying the system's radar could provide a new way to spy on its military and that THAAD missiles could undercut China's nuclear deterrent. The country has also warned of an arms race between defensive and offensive weapons on the Korean Peninsula.

The U.S. says the THAAD system is not an offensive weapon — a point that Adm. Harris reiterated on Capitol Hill on Wednesday.

"This system is a defensive system that will help protect South Korea from ballistic missile attacks from North Korea," Harris told the House committee during Wednesday's public hearing. "It is a purely defensive system," he added, saying that the THAAD components are "aimed north" — not at China to the west.

Harris said that he takes Kim Jong Un at his word when he threatens U.S. targets. The leader has previously spoken of striking U.S. cities, and this week, North Korea threatened to sink the USS Carl Vinson aircraft carrier.

"I believe that we have to look at North Korea as if Kim Jong Un will do what he says," Harris told the panel, while acknowledging that for now, at least, there's a "capability gap" between what the North Korean leader has threatened and what his military could achieve.

But when that gap is closed, Harris also said, it would represent an "inflection point, and we're going to have to deal with that, I believe."

In South Korea, the deployment has stirred a mix of reactions, including protests and clashes with police Wednesday.

"South Korean television showed images of demonstrators in rural Seongju county, about 155 miles south of the capital, hurling water bottles at trucks carrying parts of the THAAD system," reporter Jason Strother tells NPR from Seoul. "Reports say protesters tried to block its delivery to a golf course that's being converted into a base."</s>A U.S. missile defense system that's now being installed in South Korea will be operational "in the coming days," says Admiral Harry Harris, commander of the U.S. Pacific Command.

President Trump and Defense Secretary James Mattis have said all options are on the table to counter what Harris today called "the reckless North Korean regime" in testimony to the House Armed Services Committee. But Harris also stated, "We want to bring Kim Jong Un to his senses, not to his knees."

Hours before the admiral spoke to members of Congress, parts of the Terminal High Altitude Area Defense (THAAD) missile system began the trip to their deployment site in a rural part of South Korea.

"The overnight, unannounced operation came just six days after U.S. Forces Korea (USFK) secured the land in Seongju, North Gyeongsang Province, from the South Korean government," the Yonhap News Agency reports.

Large components of the U.S. THAAD system began landing in South Korea early last month, under an agreement that was reached last July.

Today's convoy of trucks and equipment included some 20 trucks, the Korea Herald reports, adding, "Although covered by plastic boxes and wrapping, they were believed to include a radar, launchers, interceptors, a fire control and communications unit, a power generator and a cooler."

Harris testified ahead of an unusual meeting at the White House Wednesday, when all 100 U.S. senators are expected to attend a classified briefing on North Korea.

China has opposed the deployment, saying the system's radar could provide a new way to spy on its military and that THAAD missiles could undercut China's nuclear deterrent. The country has also warned of an arms race between defensive and offensive weapons on the Korean Peninsula.

The U.S. says the THAAD system is not an offensive weapon — a point that Admiral Harris reiterated on Capitol Hill today.

"This system is a defensive system that will help protect South Korea from ballistic missile attacks from North Korea," Harris told the House committee during Wednesday's public hearing. "It is a purely defensive system," he added, saying that the THAAD components are "aimed north" — not at China to the west.

Harris said that he takes Kim Jong Un at his word when he threatens U.S. targets. The leader has previously spoken of striking American cities, and this week, North Korea threatened to sink the USS Carl Vinson aircraft carrier.

"I believe that we have to look at North Korea as if Kim Jong Un will do what he says," Harris told the panel, while acknowledging that for now, at least, there's a "capability gap" between what the North Korean leader has threatened and what his military could achieve.

But when that gap is closed, Harris also said, it would represent an "inflection point, and we're going to have to deal with that, I believe."

In South Korea, the deployment has stirred a mix of reactions, including protests and clashes with police Wednesday.

"South Korean television showed images of demonstrators in rural Seongju county, about 155 miles south of the capital, hurling water bottles at trucks carrying parts of the THAAD system," reporter Jason Strother tells NPR from Seoul. "Reports say protestors tried to block its delivery to a golf course that's being converted into a base."</s>A U.S. missile defense system that's now being installed in South Korea will be operational "in the coming days," says Adm. Harry Harris, commander of the U.S. Pacific Command.

President Trump and Defense Secretary James Mattis have said all options are on the table to counter what Harris called "the reckless North Korean regime" in his testimony Wednesday before the House Armed Services Committee. But Harris also stated, "We want to bring Kim Jong Un to his senses, not to his knees."

Hours before the admiral spoke to members of Congress, parts of the Terminal High Altitude Area Defense missile system, or THAAD, began the trip to their deployment site in a rural part of South Korea.

"The overnight, unannounced operation came just six days after U.S. Forces Korea (USFK) secured the land in Seongju, North Gyeongsang Province, from the South Korean government," the Yonhap News Agency reports.

Large components of the U.S. THAAD system began landing in South Korea early last month, under an agreement that was reached last July.

Wednesday's convoy of trucks and equipment included some 20 trucks, the Korea Herald reports, adding, "Although covered by plastic boxes and wrapping, they were believed to include a radar, launchers, interceptors, a fire control and communications unit, a power generator and a cooler."

Harris testified ahead of an unusual meeting at the White House on Wednesday, when all 100 U.S. senators are expected to attend a classified briefing on North Korea.

China has opposed the deployment, saying the system's radar could provide a new way to spy on its military and that THAAD missiles could undercut China's nuclear deterrent. The country has also warned of an arms race between defensive and offensive weapons on the Korean Peninsula.

The U.S. says the THAAD system is not an offensive weapon — a point that Adm. Harris reiterated on Capitol Hill on Wednesday.

"This system is a defensive system that will help protect South Korea from ballistic missile attacks from North Korea," Harris told the House committee during Wednesday's public hearing. "It is a purely defensive system," he added, saying that the THAAD components are "aimed north" — not at China to the west.

Harris said that he takes Kim Jong Un at his word when he threatens U.S. targets. The leader has previously spoken of striking U.S. cities, and this week, North Korea threatened to sink the USS Carl Vinson aircraft carrier.

"I believe that we have to look at North Korea as if Kim Jong Un will do what he says," Harris told the panel, while acknowledging that for now, at least, there's a "capability gap" between what the North Korean leader has threatened and what his military could achieve.

But when that gap is closed, Harris also said, it would represent an "inflection point, and we're going to have to deal with that, I believe."

In South Korea, the deployment has stirred a mix of reactions, including protests and clashes with police Wednesday.

"South Korean television showed images of demonstrators in rural Seongju county, about 155 miles south of the capital, hurling water bottles at trucks carrying parts of the THAAD system," reporter Jason Strother tells NPR from Seoul. "Reports say protesters tried to block its delivery to a golf course that's being converted into a base."</s>A U.S. missile defense system that's now being installed in South Korea will be operational "in the coming days," says Adm. Harry Harris, commander of the U.S. Pacific Command.

President Trump and Defense Secretary James Mattis have said all options are on the table to counter what Harris called "the reckless North Korean regime" in his testimony Wednesday before the House Armed Services Committee. But Harris also stated, "We want to bring Kim Jong Un to his senses, not to his knees."

Hours before the admiral spoke to members of Congress, parts of the Terminal High Altitude Area Defense missile system, or THAAD, began the trip to their deployment site in a rural part of South Korea.

"The overnight, unannounced operation came just six days after U.S. Forces Korea (USFK) secured the land in Seongju, North Gyeongsang Province, from the South Korean government," the Yonhap News Agency reports.

Large components of the U.S. THAAD system began landing in South Korea early last month, under an agreement that was reached last July.

Wednesday's convoy of trucks and equipment included some 20 trucks, the Korea Herald reports, adding, "Although covered by plastic boxes and wrapping, they were believed to include a radar, launchers, interceptors, a fire control and communications unit, a power generator and a cooler."

Harris testified ahead of an unusual meeting at the White House on Wednesday, when all 100 U.S. senators are expected to attend a classified briefing on North Korea.

China has opposed the deployment, saying the system's radar could provide a new way to spy on its military and that THAAD missiles could undercut China's nuclear deterrent. The country has also warned of an arms race between defensive and offensive weapons on the Korean Peninsula.

The U.S. says the THAAD system is not an offensive weapon — a point that Adm. Harris reiterated on Capitol Hill on Wednesday.

"This system is a defensive system that will help protect South Korea from ballistic missile attacks from North Korea," Harris told the House committee during Wednesday's public hearing. "It is a purely defensive system," he added, saying that the THAAD components are "aimed north" — not at China to the west.

Harris said that he takes Kim Jong Un at his word when he threatens U.S. targets. The leader has previously spoken of striking U.S. cities, and this week, North Korea threatened to sink the USS Carl Vinson aircraft carrier.

"I believe that we have to look at North Korea as if Kim Jong Un will do what he says," Harris told the panel, while acknowledging that for now, at least, there's a "capability gap" between what the North Korean leader has threatened and what his military could achieve.

But when that gap is closed, Harris also said, it would represent an "inflection point, and we're going to have to deal with that, I believe."

In South Korea, the deployment has stirred a mix of reactions, including protests and clashes with police Wednesday.

"South Korean television showed images of demonstrators in rural Seongju county, about 155 miles south of the capital, hurling water bottles at trucks carrying parts of the THAAD system," reporter Jason Strother tells NPR from Seoul. "Reports say protesters tried to block its delivery to a golf course that's being converted into a base."</s>A US missile strike on North Korea "would have absolutely cataclysmic, disastrous consequences," the former US ambassador to China has warned.

Max Baucus, who was the US ambassador to China for President Barack Obama, said it "should not be categorically discounted" that President Donald Trump could order an attack on the authoritarian state.

"After all President Trump ordered that strike on Syria, and he's a macho kind of guy, which makes all of us a bit nervous," the former senator told BBC Radio 4's Today Programme.

"But I'm sure that the Pentagon and state department, all his advisers have explained to him that a missile strike initiated by the United States at this time would have absolutely cataclysmic, disastrous consequences and I think he's wise enough not to want to have that on his watch."

North Korea conducted live-fire artillery drills and a US guided-missile submarine arrived in South Korea on Tuesday, as the Trump administration prepared what Mr Baucus called an "extraordinary" White House briefing for all 100 senators on the escalating nuclear threat.

They will be briefed by Secretary of Defence James Mattis, US Secretary of State Rex Tillerson, Director of National Intelligence Dan Coats and General Joseph Dunford.

"During the roughly 40 years I served in Congress I never remember a meeting of 100 members going to the White House on a national security issue," Mr Baucus said.

"I can only surmise the president is trying to set the stage for action he may take later, that may be diplomatic action, it might be military. It's extraordinary, I'm very surprised by this."

When asked if Mr Trump had called the meeting to capture a sense of theatre and support for military action, Mr Baucus cautioned: "That's possible but let's remember our president is quite theatrical anyway. He makes quite bold statements.

"That's his wont, that's his style, so I would discount that a bit."

He said the previous American policy of "strategic patience really hasn't worked very well," and said the US had been "a bit too patient while Kim Jong-un builds up his nuke and his missiles and China hasn't done very much."

"It is proper to ramp up the pressure," he added.

Asked whether the "big carrot" could be a face-to-face meeting with Mr Trump, Mr Baucus said: "You know I think we're getting closer to that. That's a bit down the road yet.

"We have to start thinking about diplomacy much more seriously than we have in the past."

He said the US had made some progress with North Korean diplomacy under the Clinton administration, but that broke down after the 9/11 terror attacks during the Bush administration.

"But now is the time to think about sitting down. I would not rule it out."

He said previous US administrations had been afraid to sit down with the North Korean dictator over fears he would "use it to berate us, just to talk and outmanoeuvre us," but Mr Baucus said he thinks diplomatic negotiations have become much more important.

"It's better than the alternative, the alternative is a a missile strike from one or the other, and that is clearly is catastrophpic."

His opinion was shared by retired US army special forces colonel David S Maxwell, who previously told The Independent the US has a Massive Ordnance Penetrator (Mop) bomb, developed with North Korea's underground facilities in mind.

“There are many targets in the world buried deeply underground and the Mop was developed for that,” he said. “But I think you have to ask the question: Can a military action against North Korea not result in a catastrophic response by the North?”

Fears North Korea would mark the 85th anniversary of its military's founding with a nuclear test explosion or a ballistic missile launch proved unfounded. But the unpredictable Communist nation rattled its sabre all the same, staging its largest-ever artillery firing drill that served as a reminder of the threat it poses to US-allied South Korea.

The exercise in the area of east coast city of Wonsan involved 300 to 400 artillery pieces, South Korea's Yonhap news agency said. An official from Seoul's Defense Ministry couldn't confirm such details. Seoul lies only 25 miles from the demilitarised zone separating the two Koreas, well within artillery range.

Mr Trump has sent more US military assets to the region in a show of force while leaning on China to "properly deal" with its wayward ally's continued violations of UN sanctions.

"We are probably in one of the most challenging situations since the Cuban missile crisis," Senator John McCain, who joined Mr Trump for dinner on Monday night, told a congressional hearing on Tuesday, referring to the 1962 standoff with the Soviet Union that pushed the superpowers close to nuclear confrontation.

Mr McCain said a North Korean nuclear missile capable of striking an American city was "an imminent danger."

He said Mr Trump is "exploring all options" on North Korea and added that a pre-emptive strike "would be the last one."

North Korea routinely accuses the US of readying for an invasion, and threatens pre-emptive strikes to stop it.

The state's news agency reported that unnamed Foreign Ministry spokesman said the US administration's policy to maximise pressure on North Korea was "little short of lighting the fuse of total war".</s>A U.S. missile defense system that's now being installed in South Korea will be operational "in the coming days," says Adm. Harry Harris, commander of the U.S. Pacific Command.

President Trump and Defense Secretary James Mattis have said all options are on the table to counter what Harris called "the reckless North Korean regime" in his testimony Wednesday before the House Armed Services Committee. But Harris also stated, "We want to bring Kim Jong Un to his senses, not to his knees."

Hours before the admiral spoke to members of Congress, parts of the Terminal High Altitude Area Defense missile system, or THAAD, began the trip to their deployment site in a rural part of South Korea.

"The overnight, unannounced operation came just six days after U.S. Forces Korea (USFK) secured the land in Seongju, North Gyeongsang Province, from the South Korean government," the Yonhap News Agency reports.

Large components of the U.S. THAAD system began landing in South Korea early last month, under an agreement that was reached last July.

Wednesday's convoy of trucks and equipment included some 20 trucks, the Korea Herald reports, adding, "Although covered by plastic boxes and wrapping, they were believed to include a radar, launchers, interceptors, a fire control and communications unit, a power generator and a cooler."

Harris testified ahead of an unusual meeting at the White House on Wednesday, when all 100 U.S. senators are expected to attend a classified briefing on North Korea.

China has opposed the deployment, saying the system's radar could provide a new way to spy on its military and that THAAD missiles could undercut China's nuclear deterrent. The country has also warned of an arms race between defensive and offensive weapons on the Korean Peninsula.

The U.S. says the THAAD system is not an offensive weapon — a point that Adm. Harris reiterated on Capitol Hill on Wednesday.

"This system is a defensive system that will help protect South Korea from ballistic missile attacks from North Korea," Harris told the House committee during Wednesday's public hearing. "It is a purely defensive system," he added, saying that the THAAD components are "aimed north" — not at China to the west.

Harris said that he takes Kim Jong Un at his word when he threatens U.S. targets. The leader has previously spoken of striking U.S. cities, and this week, North Korea threatened to sink the USS Carl Vinson aircraft carrier.

"I believe that we have to look at North Korea as if Kim Jong Un will do what he says," Harris told the panel, while acknowledging that for now, at least, there's a "capability gap" between what the North Korean leader has threatened and what his military could achieve.

But when that gap is closed, Harris also said, it would represent an "inflection point, and we're going to have to deal with that, I believe."

In South Korea, the deployment has stirred a mix of reactions, including protests and clashes with police Wednesday.

"South Korean television showed images of demonstrators in rural Seongju county, about 155 miles south of the capital, hurling water bottles at trucks carrying parts of the THAAD system," reporter Jason Strother tells NPR from Seoul. "Reports say protesters tried to block its delivery to a golf course that's being converted into a base."
A South Korean adviser says it is "impossible" for South Korea to purchase the THAAD missile complex since control of its operation would remain with the United States. The remarks come after United States president Donald Trump suggested that South Korea pay for the $1 billion system.