North Korea was slipping deeper into isolation this week as its neighbours prepared to introduce tough financial and weapons sanctions agreed by the UN security council.
In an unusual show of regional unity, Japan, South Korea, China and Russia lined up to back the US-drafted measures, which aim to punish Pyongyang for its nuclear bomb test last Monday.
In its first official response to the sanctions, North Korea said it wanted "peace but is not afraid of war" and that it would "deal merciless blows" against anyone who violated its sovereignty. "It is quite nonsensical to expect the DPRK [North Korea] to yield to the pressure and threat of someone at this time when it has become a nuclear weapons state," a statement said.
Air samples containing radioactive materials confirmed that the explosion had been nuclear, the office of the US national intelligence director, John Negroponte, said.
Despite the general agreement at the UN, differences of approach were becoming evident in the implementation of the punitive steps agreed, which prohibit trade in any material that could be used in weapons of mass destruction, ban sales of heavy conventional weapons and luxury goods, and call for a freeze on all accounts related to Pyongyang's nuclear, biological and chemical weapons programmes.
Japan, Washington's closest ally in the region, announced that it may introduce even tougher measures of its own. The prime minister, Shinzo Abe, said: "We are already considering them, and we want to make a final decision." The foreign ministry in Tokyo said the Japanese navy could take part in US missions to stop and search North Korean vessels.
China called for calm and emphasised that the UN resolution did not permit military force. Academics said Beijing is reluctant to check all cargo crossing its border with North Korea or to take any step that might lead to a collapse of its neighbour and an exodus of refugees. "China will carry out the decision of the security council," said Zhou Yongsheng, professor at China's Foreign Affairs University. "But full inspections along our land border are unrealistic."
John Bolton, the US ambassador to the UN, said China had a "heavy responsibility" to influence North Korea's behaviour. As the North's major ally and supplier of crucial food and energy, if it were to cut that support, Mr Bolton said, it "would be powerfully persuasive".
The security council decision, which came after the US, Britain and France overcame last-minute differences with Russia and China, demands that North Korea eliminate all its nuclear weapons but, following demands by Russia and China, expressly rules out military action against the country.
President George Bush said that the security council had sent a clear message to North Korea that its claimed detonation of a nuclear bomb was unacceptable to the world. With a climbdown by the North Koreans highly unlikely, Mr Bush has sent his secretary of state, Condoleezza Rice, on a diplomatic mission to Asia this week.
