Christopher Hill, one of the architects of a landmark February disarmament deal, said the experts would go to North Korea from September 11 to 15.

"We want this disabling to take place by December 31st. So we have to look at our ideas for disabling against the actual facility," Hill told reporters. "And we thought 'the sooner, the better.'"

"There are many different ways you can disable a nuclear facility: You can drill a hole in the side of a reactor, you can fill it with cement, you can do various things, but it helps if you have a site survey, and have a look at the reactor first so that's the concept here."

The experts, who will report back to the next meeting of the full six-party talks on the issue, will work with North Korea officials on issues like "which facilities they'll have a look at," said Hill.

"It's an ambitious phase, we have a lot of work to do and I think it's a sign of the seriousness of purpose that all parties, including the North Koreans, bring to bear on this issue," he said.

Hill, the assistant US secretary of state for East Asian and Pacific affairs, said the experts were going to North Korea at the invitation of the government of leader Kim Jong-il.

They will "conduct a survey of nuclear facilities to be disabled as part of the six-party process aimed at denuclearisation of the Korean peninsula," he said. "I don't think it will be the only such trip."

The six-country talks began in 2003 and group China, Japan, Russia, the United States, North and South Korea.

North Korea has already shut down its nuclear reactor at Yongbyon under an agreement reached on February 13.

Under the deal, North Korea agreed to make a full declaration of all its nuclear programmes and disable them in return for aid, security and diplomatic guarantees, notably normalisation of ties with Washington.

Hill was here with US President George W. Bush, who was attending a summit of the 21-nation Asia Pacific Economic Cooperation (APEC) forum.

Bush has already met here with three of his six-party partners, Chinese President Hu Jintao, Russian President Vladimir Putin, and South Korean President Roh Moo-hyun.

He was to meet Saturday with Japanese Prime Minister Shinzo Abe.

After his meeting with Roh, Bush signalled that he would support a formal declaration ending the 1950-1953 Korean War -- halted by an armistice rather than a peace treaty and therefore technically still under way -- if Pyongyang dismantles its nuclear weapons programme.

"We look forward to the day when we can end the Korean War. That will happen when Kim Jong-il verifiably gets rid of his weapons programmes and his weapons," said the US president.

Asked to comment, Chinese Foreign Ministry spokesman Liu Jianchao said that matter could be discussed at the six-nation forum.

"It can be discussed in the working groups," he said, "as we make progress in the six-party talks and move towards the realisation of the denuclearisation of the Korean peninsular we can discuss everything."

"But we should take one bite at a time, take one step at a time. We can't solve all problems all at once."

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