It has also objected to US plans for detailed inspections and searches as part of the verification process which it says would be a violation of its dignity.

As a consequence, last month North Korea announced it had stopped work on disabling its main nuclear plant at Yongbyon, barring UN inspectors from the site and announcing plans to restart the main reactor.

Face-saving

On Friday Christopher Hill, the chief US negotiator in North Korea's nuclear programme, was expected to wrap up a visit to the North after spending an extra day in negotiations with senior North Korean officials aimed at salvaging the disarmament deal.

Hill was expected to table a face-saving suggestion for Pyongyang to submit to China – North Korea's closest ally - its version on how its nuclear declaration should be verified, according to an AFP report citing US officials.

However, with communications into North Korea difficult US officials said it was unclear how North Korean officials had reacted to the proposal.

"The ball is really in the North Koreans' court," McCormack told reporters at the state department on Thursday.

In separate comments an unnamed senior US official said Condoleezza Rice, the Secretary of State, was not prepared to compromise on the demand for strict verification of Pyongyang's nuclear programme.

"From her point of view, they meet the criteria or they don't and there is nothing inevitable about this process," the official said, speaking on condition of anonymity.

North Korea, which tested an atomic weapon in October 2006, had agreed to disable its nuclear programme in return for aid and other concessions under a pact with South Korea, China, Japan, Russia and the US.