South Korea and China joined calls for North Korea to return to the negotiating table after the communist state announced it had nuclear weapons and had pulled out indefinitely from disarmament talks.
The move by North Korean presents a major challenge to US President George W. Bush, starting his second term with a policy aimed at ending Asia's nuclear crisis through the six-party talks that China has been shepherding for nearly two years.
South Korea lies under constant threat from a neighbour that keeps 70 per cent of its 1.2-million-strong army along a border that passes just 65 kilometres north of the capital, Seoul.
"The assessment is that North Korea may be trying to raise its negotiating stakes," Vice Foreign Minister Mr Lee Tae-shik was quoted as saying. "But it could turn into a very serious problem if the North takes additional steps."
North Korea's Foreign Ministry said yesterday the state had been forced to boost its defences and to acquire nuclear weapons to contend with US hostility and the policy of the Bush administration to seek regime change.
It pulled out of the six-way talks, which also involve the United States, China, Russia, Japan and South Korea, but left the door open slightly to a possible resumption of negotiations.
South Korean officials swiftly joined their US counterparts in saying talks were the only solution to end the North's isolation.
They said the news only confirmed what was already known about the North's nuclear ambitions.