North Korea's threat of a possible nuclear test has overshadowed the latest round of six-party talks in Beijing.
By Jonathan Marcus
BBC diplomatic correspondent
The talks are aimed at resolving the problem of North Korea's nuclear weapons programme.
Still talking, but sides remain far apart
But Pyongyang's rhetoric is not new.
Behind the scenes there are signs that some modest progress might be made and the broad lines of a potential future deal are becoming clearer.
Experts believe that North Korea could have as many as eight nuclear weapons and that it retains the capacity to make many more.
Any move by the Pyongyang government to conduct a nuclear test would alter the whole Asian security landscape.
Other countries like Japan, South Korea and even Taiwan might look again at their non-nuclear status.
Tensions in the region would inevitably increase.
However this sort of rhetoric has been heard from North Korea before.
It may well be intended to concentrate minds at the six-party talks, though few of the parties probably need any reminding that the stakes are high.
US under pressure
The Bush administration has been deeply divided on the stance to take towards North Korea with the state department urging dialogue and the Pentagon and the vice-president's office urging caution if not outright hostility towards Pyongyang.
Washington has seized upon the six-party formula as a way of maintaining dialogue without having to hold face-to-face bilateral talks with the North Koreans.
Nonetheless this latest round of talks is noteworthy for a significant re-packaging of the Bush administration's proposals.
Washington is under huge pressure from Japan and South Korea - its main allies in the region - to show greater flexibility.
The new plan involves immediate rewards for North Korea - heavy fuel oil imported from South Korea - if it agrees to dismantle its nuclear weapons programme.
The new plan is presented by US diplomats as a way to test North Korea's true intentions.
Washington's nightmare is not so much a nuclear-armed North Korea but the fear that Pyongyang could transfer nuclear technology to other countries or even to terrorist groups.