"The two sides are like accelerating trains coming towards each other with neither side willing to give way." That was how China's Foreign Minister Wang Yi described the tension between the United States and North Korea. The fact that the drivers of the two trains are Kim Jong Un and Donald Trump will not reassure those of a nervous disposition.
Last weekend, the US train gave a toot on its whistle, as Secretary of State Rex Tillerson announced that the era of American "strategic patience" with North Korea is over. He also made a point of emphasising that America is considering all options, including military strikes.
Mr Tillerson's statement reflected a bipartisan consensus in the US that North Korea's nuclear ambitions must be stopped. The Kim regime is widely believed to be closing in on developing an intercontinental ballistic missile (ICBM) that could threaten the west coast of the US. It is conventional wisdom in Washington that no president could tolerate such a situation. The implication of Mr Tillerson's statement is that, if the US cannot stop North Korea through diplomatic or economic pressure, it will have to take military action.
But the idea of bombing the North Korean nuclear programme is dangerous folly. For the past 20 years, the US has repeatedly considered the idea and repeatedly dismissed it - for good reason.
The North Korean nuclear and missile programmes are widely dispersed, including underground and underwater. It is unlikely that the whole programme could be destroyed in a single wave of strikes, which would immediately raise the prospect of nuclear retaliation by Pyongyang.
Even if the US was miraculously able to take out the whole nuclear programme in one swoop, the North Koreans still have formidable conventional artillery. They could launch devastating barrages aimed at Seoul, the South Korean capital, a city of 10 million people just 56km from the North Korean border. Japan would also be vulnerable to missile strikes, as would US bases in the region.
But the best ways of dealing with (the North Korean nuclear) threat are diplomatic and economic, not military... Efforts at striking a "grand bargain" with the Kim regime might still fail. But even if diplomacy fails, the right alternative is not to launch a war.
For that reason, the US would be unlikely to have the support of its key Asian allies if it staged a pre-emptive strike against North Korea. Tokyo and Seoul know that a war on the Korean peninsula could cost more than one million lives. It could also draw in China, which is both a neighbour and a formal treaty ally of North Korea. It is worth remembering that the last time American and Chinese troops fought each other was on the Korean peninsula in the 1950s.
So the idea that America "cannot tolerate" a North Korean nuclear ICBM needs to be challenged. Ever since the 1960s, the US has lived with the knowledge that Russia has nuclear missiles that could annihilate much of the country. Today, America and its allies have to live with the knowledge that Pakistan, a country that is the base for some of the most dangerous Islamist movements in the world, is churning out nuclear weapons.
Some argue that Pyongyang's case is different because Mr Kim is "mad". But claims that a foreign leader is crazy are a sure sign of lazy thinking - of the kind that led the West to disaster in Iraq and Libya. Mr Kim is evil, ruthless and isolated. But there is a consistent thread that runs through his actions, and that is an absolute determination to ensure the survival of his regime. It is this that explains the murder of any possible rivals, the relentless drive to secure a nuclear deterrent and the willingness to impose economic privation on his people. Given that survival is the North Korean leader's absolute priority, there must be considerable doubt that even intensified economic sanctions can persuade him to abandon his nuclear programme. In fact, the threat of regime collapse might make North Korea even more dangerous.
None of that suggests that the US should fatalistically accept that North Korea will acquire a nuclear capability that can threaten California. But the best ways of dealing with that threat are diplomatic and economic, not military.
The Trump administration thinks China holds the key to North Korea. It is certainly true that the regime in Pyongyang is economically dependent on its neighbour to the north. The Chinese have also shown some willingness to tighten economic sanctions on North Korea by stopping imports of coal.
It might make sense to apply economic pressure on North Korea in the short term. But the better route, in the long run, would be to search for a deal that freezes the country's nuclear programme, in return for economic assistance and a guarantee that the US will not seek to overthrow the regime. This is what academic John Delury, a leading specialist on North Korea, has termed a "grand bargain".
Any diplomatic feelers to the North Korean regime would have to be made in secret, initially, and might involve enlisting Chinese support. Efforts at striking a "grand bargain" with the Kim regime might still fail. But even if diplomacy fails, the right alternative is not to launch a war. America would just have to live with the threat of North Korean nuclear weapons, as it has lived with similar threats in the past. Otherwise, we may indeed be heading for a deadly train crash.
THE FINANCIAL TIMES