As the crisis over North Korea’s nuclear weapons programme has intensified, the focus of many outsiders has shifted from the country’s leader – often and inaccurately described as crazy – to US policy on the issue.

In recent days there have been reports suggesting the US might attempt to solve the crisis through military means. Last month, the British newspaper The Telegraph reported the Trump administration was considering a surgical strike on North Korea’s nuclear or missile infrastructure. A Wall Street Journal story on December 9 made the same claim.

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Simultaneously, however, US President Donald Trump has said he welcomes talks with North Korea to settle the problem peacefully. According to a South Korean press report, Trump said The Wall Street Journal report was “completely wrong” during his telephone conversation with South Korean President Moon Jae-in.

Within the last week, Trump has said “talks are a good thing!”, “I always believe in talking”, and he would be “absolutely” willing to talk to the North’s leader Kim Jong-un. Trump’s White House office said the American president favours such talks “at the appropriate time, under the right circumstances”.

This may seem a confusing set of mixed signals but there is more coherence than meets the eye if we understand the bigger picture. Going back to the 1990s and even earlier, the essence of US policy toward North Korea can be explained by three fundamentals.

First, the immediate and overwhelming American concern is preventing North Korea from acquiring nuclear missile capabilities.

Second, Washington is willing to negotiate with Pyongyang if it first acknowledges that denuclearisation is on the agenda. This is what the White House means by “the right circumstances”.

Third, the United States will attempt to persuade Pyongyang to enter negotiations under this precondition through pressure and isolation. The Trump administration calls this “maximum pressure”. It includes not only tough economic and diplomatic sanctions, but also the threat of military action.

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For many years, Washington’s message has been that North Korea will receive a reward for good behaviour but punishment for bad behaviour. The Trump administration’s actions and statements, including Trump’s tweets, fit within this approach. Trump on one hand has called Kim a dangerous madman but on the other hand said he would like to meet Kim for lunch over hamburgers. US policy toward the North is not schizophrenic. Both carrot and stick are necessary parts. Currently at issue is the precise form of positive and negative inducements.

On the positive side, the question relates to the concessions Washington should make to Kim’s government. The US has agreed to suspend annual joint military exercises with ally South Korea during the Olympics, which likely cleared the way for Pyongyang to request talks with Seoul about North Korea’s participation in the Games. But the US government has reiterated negotiations cannot begin unless North Korea agrees to put its nuclear weapons on the bargaining table.

As for negative inducements, since the most pressing goal of US policy is to prevent Kim’s regime from deploying a nuclear missile, as North Korea edges closer to this objective, so too will the punitive aspects of US policy intensify.

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Increasingly tough sanctions have not forced Pyongyang to change course. Beijing has proved unwilling to squeeze the North too forcefully for fear of causing the regime to collapse. Consequently, Washington considers the military option, and tells Pyongyang so in the hope of deterring it from completing their weapons programme.

The prospect of military action pits US and South Korean security interests against each other. The North could potentially cause massive casualties and damage in Seoul, which is within range of thousands of Kim’s artillery guns and rocket launchers. If hit with a US surgical strike, Kim might retaliate by pummelling Seoul.

This fear is increased by the possibility that senior North Korean military leaders are overconfident in their presumed invulnerability to US attack, and by the concern that Kim would not be able to distinguish a limited strike from the beginning of an all-out war aimed at overthrowing his regime. On the other hand, one could make a reasonable case that Kim would not retaliate by attacking Seoul because he knows that would guarantee the demise of his regime and himself.

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Such cold logic is easier to accept in Washington – which for the moment remains safe from the North’s ordnance – than in Seoul. To keep his campaign promise that a North Korean nuclear missile “won’t happen”, Trump might be tempted to take a gamble for which South Koreans will assume most of the risk.

Denny Roy is a senior fellow at the East-West Centre in Honolulu, Hawaii