Christopher Hill, the chief US envoy to the negotiations, would not say what was in the four-page document, but said it included sections on sampling and visits as part of a verification plan.

"We need a verification process that's clear and that does not leave ambiguity, and that certainly, I think, is what the draft tries to address and what we tried to address in our comments,'' he told The Associated Press.

Kim Sook, South Korea's lead negotiator, said the parties were still working on the language in the draft.

'Avoiding ambiguity'

"We are making efforts to dispel misunderstandings brought by ambiguous expressions, and reach an agreement by replacing them with transparent ones,'' Kim said.

Hill said on Tuesday that he had gone to Beijing with "three goals in mind".

He said the pressure was on delegates to agree on specific standards by which to check if North Korea has told the truth about its past nuclear activities; to set schedules for delivering fuel aid to the North; and to agree on a timetable for disabling its nuclear facilities.

North Korea agreed in 2007 to end its nuclear weapons programme in return for aid
The US and North Korea differ on what was agreed when Hill visited Pyongyang in October to try to salvage a disarmament deal struck in February 2007.

After reaching an apparent deal on verification procedures, the US announced it would drop the North from its so-called "terrorism blacklist".

The North then backed down from its threats to restart its plutonium-producing nuclear plants.

However, North Korea, which tested a nuclear weapon in October 2006, insists it never agreed to samples of atomic material being taken away from its nuclear sites.

Pyongyang has previously said the outside verification of its nuclear inventory will involve only field visits, confirmation of documents and interviews with technicians.

The six-party talks bring together negotiators from the US, China, Russia, Japan as well as North and South Korea.

Hill is attempting to seal a rare diplomatic success for the outgoing US administration in the final days of the Bush presidency.

But observers say a breakthrough is unlikely with Pyongyang expected not to make any serious moves until Barack Obama, the US president-elect, takes office.

In one sign of progress however, a consensus had been reached on Monday to complete the shipment of all promised economic aid to North Korea.

This includes one million tons of fuel oil or equivalent energy aid by the end of March.

Although a signatory to the six-nation disarmament deal, Japan has refused to send any aid to North Korea, demanding that Pyongyang first address the kidnappings of more than a dozen Japanese nationals during the Cold War.