NORTH KOREA has few cards to play in international politics. Yet the isolated communist state is now brandishing what appears to be its ace, saying it will test a nuclear weapon and spreading disquiet in Asia and beyond. This week’s threat, apparently designed to prove a claim made last year that the country has nuclear weapons, marks a serious escalation of tension. It follows the test-launch of several missiles in July, one of which (though it failed in the test) was thought to have the range to hit Alaska.

It is unclear whether North Korea under its dictator, Kim Jong Il, really intends to conduct a nuclear test soon, but satellite monitoring suggests that preparations have been underway for months. Mr Kim craves international attention and may be banging his drum now for various reasons. He wants to put pressure on a United States government preoccupied by mid-term elections at home, distracted by violence in Iraq and struggling to deter Iran from building its own nuclear weapons. (Mr Kim may also possibly disapprove of the likely selection of South Korea’s foreign minister, Ban Ki-moon, as the UN’s new secretary-general.) Making trouble when America is distracted and widely stretched may be Mr Kim’s way to extract concessions from the superpower.

The nuclear threat is being taken seriously. Mr Kim’s regime is not near collapse, but it is under severe pressure, suffering strains at home because of poor harvests and floods and increasing isolation abroad. After the missile tests in July, the UN’s Security Council agreed to urge governments to disrupt any trade in missile parts with North Korea. Even China, long-reluctant to put serious pressure on its neighbour, supported the UN resolution.

The country's official news agency said this week that a nuclear test would be a reaction to American threats. It would also be a response to year-old financial sanctions, led by America, designed to crackdown on North Korea’s illegal efforts to get hold of hard-currency. These include traffic in illegal drugs, counterfeiting of legal drugs (like Viagra) and forging dollars, euros and yen. These are thought to be crucial to Mr Kim’s ability to keep control at home, letting him spread favours and pay for private luxuries. North Korea’s already limping economy is suffering too, as banks that once helped launder money for the communist state, for example in Macau, have frozen its accounts.

Reactions to North Korea’s latest threat have been swift. America’s secretary of state, Condoleezza Rice, called it “provocative”. Japan had already taken a more assertive line towards North Korea after the missile tests in July. Its new prime minister, Shinzo Abe, told parliament on Wednesday that his country “could not accept” a nuclear test in North Korea. South Korea's response was unusually strong. The country went on a higher security alert, and a foreign-ministry spokesman said it would not “tolerate” a nuclear test.

China’s government has appealed for calm, but is also keen to deter North Korea from conducting a test, fearing that Japan may otherwise be encouraged to seek nuclear weapons itself. There are signs of growing Chinese pressure on North Korea. China has some leverage over its neighbour, absorbing the largest share of North Korea’s paltry exports (about a third) and providing aid and energy in return. The Chinese are furious with North Korea over the missile tests in July. Some reports suggest the quantities of food and oil that China ships to its poor neighbour have been cut. Observers are also struck that China supported the Security Council resolution on North Korea and quietly imposed some financial sanctions of its own.

What will happen next is unclear. Americans and others will be pleased that Mr Kim is feeling that heat as North Korea’s counterfeiting activities are stopped. China and South Korea offer some limited leverage on Mr Kim’s regime. China is suggesting that a return to stalled talks that include America, Japan, North and South Korea, may be the only way to negotiate a resolution.