Images Show More Work at North Korean Nuclear Site SEOUL, South Korea - North Korea warned on Tuesday that it would have to take "countermeasures" if the United States insisted on sanctions, while the latest satellite imagery of the country's nuclear test site suggested heightened preparations for a possible underground nuclear test. The warning came a day after Glyn T. Davies, the top United States envoy on North Korea, said that the North would face more sanctions should it conduct a nuclear test. The Group of 8 nations issued a similar warning last week amid concerns that the North's new leadership headed by Kim Jong-un might attempt a nuclear test to boost its standing at home and regain some of the leverage it lost when a rocket failed to put a satellite into orbit in April. Washington condemned the rocket launch, calling it a test of long-range missile technology and a violation of United Nations Security Council resolutions. The Council ordered the tightening of sanctions. On Tuesday, a spokesman for North Korea's Foreign Ministry said his government "did not envisage such a military measure as a nuclear test" when it was preparing for the satellite launch. But the North said it will continue to bolster its nuclear weapons program as long as Washington remains "hostile." "If the U.S. persists in its moves to ratchet up sanctions and pressure upon us despite our peace-loving efforts, we will be left with no option but to take countermeasures for self-defense," the spokesman was quoted as saying by the state-run Korean Central News Agency. Tuesday's comments from Pyongyang conformed with its tactics of using nuclear threats to draw Washington to the negotiating table or accusing the United States of raising tensions as a way of justifying its actions, such as a possible nuclear test. "I don't know that it adds or detracts from what we already know about the North Korean view about what's happening," Mr. Davies said from Beijing, where he was meeting with Chinese officials about North Korea, The Associated Press reported. Earlier Tuesday, James Hardy, an analyst at IHS Jane's Defence Weekly said that images taken by two satellite companies, DigitalGlobe and GeoEye, in the past month showed more earth being removed from a tunnel at the Punggye-ri nuclear test site in North Korea's northeast. North Korea detonated nuclear devices underground at Punggye-ri in 2006 and 2009. In recent weeks, South Korean intelligence officials and United States analysts have reported increased activities around a newly dug tunnel, where it is expected that a nuclear test would take place should the Pyongyang leadership make the political decision to go ahead with one. Recent satellite imagery of the North's main nuclear complex at Yongbyon, north of Pyongyang, showed that the country has also resumed construction on a nuclear reactor that analysts say is part of the country's efforts to secure fuel for nuclear bombs. Also Tuesday, an analysis posted on 38 North, a Web site run by the U.S.-Korea Institute at Johns Hopkins University, said that the construction of new North Korean facilities designed to support the launches of rockets bigger than the one tested in April was making rapid progress. Citing satellite photos from April 29, it said that a new launch facility under construction since last summer at Musudan-ri on the North's northeast coast was bigger than an old facility in the same area that was used to launch long-range rockets in 1998, 2006 and 2009. It looked also bigger than a newly built launchpad in Tongchang-ri near the North's northwestern tip, where the North's Unha-3 rocket took off in April. All those rockets failed to complete their designed flights, indicating that North Korea still had a long way to go before mastering the technology needed to deliver a warhead on intercontinental ballistic missiles. Rockets launched from Musudan-ri flew over Japan and toward the Pacific, while the one taking off from Tongchang-ri flew south. Since the failure of the April launch, North Korea has said that it will continue to test its rockets, including models bigger than the Euha-3. It said its rockets program was designed to put satellites into orbit for peaceful purposes. At the current pace of construction, the new Musudan-ri facility should be operational by 2016-17, 38 North said.