North Korea is attempting to induce Washington to agree in writing to certain steps to defuse the crisis before the talks begin, the official said.

"I'm not saying that there won't be something before the talks, but you can't negotiate the round before the round," the official said on condition of anonymity.

"You have to leave some things for the talks."

One issue vital to hopes of resolving the nuclear crisis is "sequencing" -- the order of steps Pyongyang and Washington would both agree to take to defuse the crisis.

Under one scenario, which the Wall Street Journal said was part of a Chinese drafted framework, Pyongyang would renounce nuclear weapons, and Washington would quickly follow up with a formal US pledge not to attack North Korea.

A broader array of other steps, including the possibility of diplomatic relations between the two Cold War foes would follow, the report said.

The official said that such questions needed to be negotiated within the six-nation dialogue, and could simply be agreed to before it started.

"The sequence is just one idea that's out there. The Chinese are not saying that if we don't sign up for this there won't be talks but they are telling us that this is what the North Koreans want.

"The North Koreans are trying to get things on paper before the talks even begin."

"We have got to find a way to get North Korea to the table and that's what we're doing," said the official, explaining the complicated blizzard of diplomacy between the parties, North and South Korea, Japan, Russia, the United States and China, preceding the talks.

Negotiations aim to persuade Pyongyang to abandon its nuclear programme.

Signs emerged from Washington and Asia in the last few days that wrangles on the substance of the talks would likely push them back to January or February.

The crisis erupted after Washington said in October last year that North Korea had broken a 1994 nuclear freeze agreement by embarking on an enriched uranium programme.

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