The US negotiator Stephen Bosworth said: "It has been a very useful meeting. The tone was positive and generally constructive.

"I am confident that with continued effort on both sides, we can reach a reasonable basis of departure for formal negotiations for a return to the six-party process."

However, he said there was a long history of differences between them, which could not easily be overcome.

Pyongyang wants the six-party talks to restart without preconditions - but Washington wants a clear commitment first from the DPRK to disarm.

Chinese state media reported that DPRK leader Kim Jong-il has repeated that Pyongyang was willing to restart six-party talks as soon as possible.

The Xinhua news agency said Kim had told visiting Chinese Vice Premier Li Keqiang that "the principle of simultaneous action" should apply - a reiteration of the DPRK’s stance that negotiations should resume without preconditions.