"Most delegations were prepared to work on the Chinese text [and] there was a consensus on how to move forward. That consensus was not shared by the DPRK[The Democratic People's Republic of Korea]."

The Chinese delegation distributed the document on Wednesday, which was meant to be the final day of the negotiations. But a spokesman for the South Korean envoy said the talks are to continue on Thursday morning.

The US had hoped to persuade the North to allow inspectors to remove samples from their nuclear sites for analysis outside the country.

But Pyongyang has rejected such a plan, although most of the countries present at the negotiations maintain that it is obliged to allow the inspections.

Kim Sook, the South Korean enoy, told the Associated Press that "differences were not narrowed".

US assurances

Kim also said that the North Korean delegation had ruled out external inspection because they did not trust Washington.

Hill said the US was not trying to single out the North but was looking for a verification system that "works throughout the world".

"We're not looking to create some kind of North Korean exceptionalism,'' he told the Associated Press.

"We're not looking for anything new, or different. We're looking for tried and tested ways of conducting verification.''

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.

Terrorism blacklist

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.