It would not be the first time that Pyongyang's quixotic dictatorship tried to make itself heard through military pyrotechnics: in October 2006, it tested a nuclear bomb. Then, as now, its objective was to grab Washington's attention and parlay that into food, money and diplomatic concessions.

Heightened tensions on the peninsula show how far the US's once-heralded deal has slipped. In 2007, Pyongyang promised to disable much of its nuclear programme and provide information on the rest. It was rewarded, despite at best partial compliance, when Washington removed it from a list of state sponsors of terrorism. Since then, the process has drifted badly.

Mr Obama must now decide where to place reviving talks on his list of foreign policy priorities. Pyongyang is already jostling for attention with the Middle East, Afghanistan and Indo-Pakistan tensions, not to mention Iran's own nuclear ambitions. To give Mr Kim attention would be to reward his regime's threats. Yet to ignore him would be to provide Pyongyang with more time to develop a fully fledged nuclear capacity, assuming it does not have one already.