I was in Seoul the other day. In London politicians were arguing about whether Britain should sue for divorce from its European partners. In South Korea the conversation was about when its northern neighbour would choose to test-fire another missile and explode another nuclear bomb. Europe has its problems. They can look small against the challenges elsewhere.

It is commonplace to say the history of the 21st century will be written in Asia. Whether it is peaceful or otherwise will probably depend on whether the US and China can avoid inevitable competition turning into an uncontrolled collision. The handling by the two great powers of Kim Jong Un’s despotic regime in North Korea is an important test; with a different mindset it could also be an opportunity.

The omens are not encouraging. Sino-Japanese tensions in the East China Sea sit next to Beijing’s maritime assertiveness as it solidifies its territorial claims in the South China Sea and alongside Mr Kim’s declared aim of turning North Korea into a fully fledged nuclear weapons state. The straits of Taiwan are an enduring potential flashpoint. Military spending in the region has surpassed that of Europe.

So when the Asan Institute, South Korea’s leading foreign policy think-tank, convened its latest conference, it took as a title “The New Normal”. The organising assumption confronting this annual gathering of scholars and policymakers from across the region and beyond was that rising tensions and insecurities were being woven deep into the fabric of the geopolitics of East Asia. There were few voices raised against the notion. Europeans were left with the unnerving feeling that the Asian powers are destined to make the same mistakes during this century that Europe made during the first half of the last.

The Pyongyang regime offers a chilling expression of the dangers. In recent days Mr Kim has been presiding over the first gathering in a generation of North Korea’s Workers’ Party. The goal has been to entrench his position as supreme leader and to boast about what he told the opening session of the Congress were the country’s “magnificent and exhilarating” advances in nuclear and missile technology.

The US and China have the same strategic objective so far as Mr Kim is concerned: they want him to call a halt to the nuclear programme and to stop developing ballistic missiles. Beijing has no interest in blessing a second nuclear power in East Asia, while Washington knows that Pyongyang wants to develop a missile capable of carrying a nuclear warhead to the west coast of the US. Mr Kim’s unpredictably combustible personality — he is one of the few leaders around the world who make Donald Trump look level-headed — adds to the danger.

So both countries supported February’s UN Security Council resolution significantly toughening sanctions against the regime in response to the country’s fourth nuclear test at the start of the year. But here Sino-American co-operation reaches its limits. Much as Beijing is enraged by Mr Kim’s antics, which, apart from anything else, deeply insult the authority of President Xi Jinping, it views North Korea as a buffer state.

Collapse of the regime and reunification of the peninsular would carry the prospect of a US-allied Korea on China’s doorstep. So, as I heard several times at the Asan conference, Beijing will not consent to any international action that threatens North Korea’s survival.

Beijing’s answer is to argue for the sanctions to be combined with a resumption of the long-abandoned six-party talks with Pyongyang — negotiations that included South Korea, Japan and Russia as well as China and the US. Mr Kim, Chinese officials say, is serious about the economic modernisation of North Korea. For his programme to work, he needs investment and technology. That gives the international community leverage.

The US — and, it should be said, the South Korean view — is unconvinced. As long as Mr Kim knows that he can rely on China to prop up his rule he has no real incentive to negotiate. Western estimates suggest he already has a stockpile of about a dozen nuclear warheads and although Pyongyang is some years off acquiring an intercontinental ballistic missile it shows no inclination to slow the missile programme. In any event, the record of more than two decades of negotiation is dismal — for Pyongyang, promises are made to be broken.

Washington’s answer is to tighten the sanctions screw as far as Beijing will permit while developing missile defences for itself and its allies against the nuclear threat. The problem, as everyone knows, is that this is essentially an excuse to kick the can a little further along the road.

For a long time it was said of the former Soviet Union that its communist system was at once unsustainable and showing no signs of cracking — until, that is, it collapsed in on itself. Something similar is probably true of North Korea. The worrying thing is what could happen in the interim.

The US and China have no choice but to live with each other in Asia. For many of China’s neighbours Washington serves as the essential guarantor of security. For its part, the US cannot ignore the fact of rising Chinese power. The choice is between mutual accommodation and conflict. North Korea is a test.

philip.stephens@ft.com

This article has been amended since publication.

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