WASHINGTON - North Korea is still moving to restart its nuclear weapons programme, US officials said Friday, despite a visit by a top US diplomat to the country to rescue a crumbling nuclear disarmament pact.

Based on information received as late as Thursday, "North Koreans continue to take some steps to reverse disablement in some of the Yongbyon facilities," said Robert Wood, a State Department spokesman.

"In essence, the only details I can give you on that is some of the equipment that was moved to storage, we are now seeing put back in place," he told reporters.

It showed North Korea was continuing efforts to resume plutonium reprocessing at the key Yongbyon nuclear reactor complex even as top US envoy Christopher Hill was in Pyongyang this week trying to revive diplomatic efforts aimed at ending its nuclear weapons drive.

Hill left Pyongyang Friday for Seoul, where he briefed his South Korean and Japanese counterparts in six-nation talks aimed at halting the North's nuclear programme.

He will leave Saturday for China, which chairs the six party talks, for meetings in Beijing with nuclear negotiator Wu Dawei and Russia's ambassador.

The International Atomic Energy Agency (IAEA) said last month that North Korea had kicked out its inspectors from the Yongbyon complex, removed its surveillance equipment there, and planned to reintroduce nuclear material.

Hill told reporters in Seoul Friday that he had "very substantive" talks in Pyongyang but gave no further details. North Korea was equally tight-lipped about the visit.

A dispute over inspections of the North's nuclear facilities threatens to wreck last year's agreement under which the North shut down the atomic programme in Yongbyon that fuels its nuclear weapons.

The hardline communist state, which tested an atomic weapon in October 2006, began disabling its aging reactor and other plants at Yongbyon in November under the pact with South Korea, China, Japan, Russia and the United States.

But it announced last month it had halted work in protest at Washington's refusal to drop it from the US blacklist of countries supporting terrorism, as promised under the deal.

Washington says the North must first accept strict outside verification of the nuclear inventory that Pyongyang handed over in June -- a key topic in Hill's discussions in Pyongyang.

US officials had said earlier Hill could offer the North a face-saving compromise in hopes of settling the verification dispute.

Under the plan, North Korea may first give China a plan that includes sampling of nuclear material, access to key atomic sites and other verification provisions sought by the United States.

President George W. Bush would then provisionally remove the North from the terrorism list, after which China would announce North Korea's acceptance of the verification plan.

This would allow Pyongyang to assert that the delisting occurred before the verification plan was in place.

Even though Hill was expected to fly back to Washington from Beijing on Saturday, Sung Kim, the special US envoy for the six-party talks, will remain in the region, Wood said, indicating diplomacy would remain active on the issue.

The question is whether the secretive North can swallow the US-inspired verification plan, which reportedly also calls for access to undeclared suspected nuclear facilities.

North Korea has accused Washington of violating its dignity by seeking Iraq-style "house searches" as part of a rigid verification protocol.

But US officials say there will be no compromise on the rigid verification measures aimed at confirming that the North's nuclear declaration was "whole and complete and verifiable."

From US Secretary of State Condoleezza Rice's point of view, "they meet the criteria or they don't and there is nothing inevitable about this process," one official said.

- AFP /ls