Now that President Bill Clinton has extricated Laura Ling and Euna Lee from North Korea, the hard work begins. There are new indications that North Korea may be transferring nuclear weapons technology to Myanmar, the dictatorship also known as Burma, and that it earlier supplied a reactor to Syria. For many years, based on five visits to North Korea and its border areas, I've argued for an 'engagement' approach toward Pyongyang, but now I've reluctantly concluded that we need more sticks. Burmese defectors have provided detailed accounts of a North Korean reactor, perhaps a mirror of the one provided to Syria, built inside a mountain deep in Myanmar. The reports, first aired in The Sydney Morning Herald this month, come from Desmond Ball, a respected Asia scholar, and Phil Thornton, a journalist with expertise on Myanmar, and there has been other fragmentary intelligence to back them up. If the defectors' accounts are true, the reactor 'could be capable of being operational and producing a bomb a year, every year, after 2014,' Ball and Thornton wrote. The suspicions may be false, and Iraq is a reminder that defector reports about WMD can be wrong. But partly because the North Korean reactor in Syria (destroyed by Israeli bombing in 2007) caught intelligence agencies by surprise, everyone is taking the latest reports seriously. Secretary of State Hillary Clinton expressed concern about the transfer of nuclear technology from North Korea to Myanmar, without giving details. All this was eerily foreshadowed by the North Koreans themselves. Michael Green, who ran Asian affairs for a time in the Bush White House, says that in March 2003, a North Korean official -- with hands shaking -- read out to him and other American officials a warning: We have a nuclear deterrent. If you don't end your hostile policy, we will demonstrate, expand and transfer it. 'They've done all those things,' Green notes. At times in the past, there seemed hope for diplomacy aimed at coaxing North Korea into giving up its nuclear program and joining the concert of nations. These days that seems virtually hopeless. 'Formal diplomatic engagement aimed at rolling back their nuclear program has run its course, at least for the time being,' says Mitchell Reiss, a North Korea expert and former senior State Department official who is now at the College of William and Mary. 'The facts have changed. You have to change your strategy.' In the past, Reiss focused on engagement. Now he advocates 'hard containment' -- toughened sanctions backed by military force if necessary. The truth is that North Korea doesn't want to negotiate away its nuclear materials. It is focused on its own transition, and this year it has declined to accept a visit from the Obama administration's special envoy, Stephen Bosworth. The North isn't interested in 'six-party talks' on nuclear issues; instead, it seeks talks with the U.S. conditioned on accepting North Korea's status as a nuclear power -- which is unacceptable. In recent months, North Korea has dismantled some economic reforms and economic cooperation projects with South Korea. Meanwhile, it continues to counterfeit U.S. $100 bills -- the highest-quality goods that North Korea manufactures -- and its embassies in Pakistan and other countries pay their way by smuggling drugs, liquor and currency. The North has released its American hostages but continues to hold South Koreans. And it's the most totalitarian state in history: In North Korean homes, I've seen the 'speaker' on the wall that wakes people up with propaganda each morning. More bizarre, triplets are routinely taken from parents and raised by the state because they are considered auspicious. There are no good options here, and a grass-roots revolution is almost impossible. North Koreans, even those in China who despise the regime, overwhelmingly agree that most ordinary North Koreans swallow the propaganda. Indeed, Kim Jong-il's approval rating in his country may well be higher than President Barack Obama's is in the United States. Our best bet will be to continue to support negotiations, including a back channel that can focus on substance instead of protocol, as well as economic and cultural exchanges -- but backed up by sticks. The Obama administration is now working with allies to reimpose economic and financial sanctions that a few years ago were very successful in squeezing the North Korean regime. China is surprisingly cooperative, even quietly intercepting several shipments of supplies useful for WMD programs. Where we have intelligence that North Korean ships are transferring nuclear materials or technology to a country like Myanmar or Iran, we should go further and board those vessels. That's an extreme step, but the nightmare would be if Iran simply decided to save time and buy a nuclear weapon or two from North Korea. We can't allow that to happen. 