NORTH KOREA is not bound by any global rules. Its hereditary dictator, Kim Jong Un, imposes forced labour on hundreds of thousands of his people and threatens to drench Seoul, the South’s capital, in “a sea of fire”. Nuclear weapons are central to his regime’s identity and survival. It has always been tempting for America and other countries to put North Korea’s nuclear ambitions on the back burner, in large part because of a chronic absence of good options for dealing with them. The history of unsuccessful responses to North Korea’s nuclear ambitions began in 1993, when Mr Kim’s father, Kim Jong Il, threatened to pull out of the nuclear Non-Proliferation Treaty (NPT) (see timeline). So when in 2010 President Barack Obama made an impassioned plea for a world without nuclear weapons, there were grounds for optimism. Although Mr Obama has made progress in many areas, from non-proliferation deals with Russia and Iran, to international summits on nuclear security, on North Korea, his failure is glaring. Under his watch the country’s nuclear-weapons and missile programme has become steadily more alarming. It is now thought to have a stockpile of around 20 devices. Every six weeks or so it adds another.

And this year the pace of ballistic missile testing has been unprecedented. An underground nuclear detonation in January, claimed by the regime to be an H-bomb (but more likely a souped-up A-bomb), has been followed by tests of the technologies behind nuclear-armed missiles. American and South Korean officials are convinced that North Korea can already make a warhead small enough to fit on the Nodong, which can reach targets in Japan and South Korea, including American bases (see map). And there are also worrying signs of progress in the development of its longer-range missiles. Although three tests of an intermediate-range 4,000-kilometre (2,500-mile) Musadan missile failed in April, North Korean engineers learn from their mistakes. Flight testing of the KN-08 intercontinental ballistic missile could begin soon and sometime during the second term of Mr Obama’s successor, these are likely to be able to strike New York. America needs worked-out plans to seize or destroy North Korea’s nuclear missiles before they can be used. China’s co-operation, or at least acquiescence, will be vital. So clear and present is the danger that even rivals who clash elsewhere in Asia must urgently find new ways to work together.

For more on North Korea's nuclear threat, read our leader, A nuclear nightmare, and our Briefing, By the rockets’ red glare.