Two teams -- one of academics and a scientist, the other from Congress -- will be in the Stalinist state at a critical point of the crisis, as China strives to bring Washington and Pyongyang plus Japan, Russia and South Korea, back to the negotiating table.

"We have nothing to do with this group or groups' reported plans to visit North Korea," said State Department deputy spokesman Adam Ereli.

"I think it should be clearly understood that the groups or individuals are not acting on behalf of the administration," Ereli said, using words echoed by the White House.

One delegation is led by a top Stanford University China expert and includes Jack Pritchard, who retired as State Department envoy to talks with North Korea last year, and nuclear scientist Sig Hecker, former director of the Los Alamos National Laboratory.

USA Today newspaper said the group would visit the Yongbyon nuclear plant, where they would be the first foreigner visitors since Pyongang expelled UN inspections a year ago.

But a member of the delegation told AFP the Yongbyon visit was still not certain.

There was also some uncertainty, fanned by Friday's publicity, over whether the team would in fact be allowed into notoriously insular North Korea at all.

A second US delegation is made up of Keith Luse, an aide to Senate Foreign Relations Committee chairman Richard Lugar, and Frank Jannuzi, who works for the ranking Democrat of the panel, Senator Joseph Biden.

But a congressional source said the second team would focus on human rights and humanitarian aid, on a trip which is a followup to previous visits to North Korea.

South Korea said earlier Friday that Pyongyang had agreed to allow a US delegation to visit between January 6-10.

Though neither delegation is endorsed by the US government, officials here would be keen for any readout from members who made it inside the Yongbyon nuclear plant.

The State Department, keeping both delegations at arms length, said it neither facilitated nor opposed the visits to North Korea.

US academics and congressional aides have made a series of unofficial visits to North Korea, but observers say none of them have reached the level of "track two" diplomacy as Pyongyang's political system lacks the sophistication for such an approach.

Pyongyang said last June that the Yongbyon plant had completed reprocessing 8,000 spent fuel rods -- thought to be enough for around six nuclear weapons -- in addition to the one or two nuclear devices US intelligence services assume North Korea already possesses.

North Korea has rejected the idea of resuming inspections in the plant, which were frozen after the fracture of a 1994 US-anti-nuclear deal, after Washington said in late 2002 that Pyongyang had embarked on a banned enriched uranium nuclear crusade.

News of the visiting US delegations follows North Korea's statement that it was ready to join delayed six-nation talks on the crisis sparked by its drive for nuclear weapons in October 2002.

While vowing to continue diplomatic arm-wrestling with the United States over the communist country's nuclear threat, Pyongyang said in a New Year's message Thursday that it was ready to peacefully resolve its nuclear crisis.

A second round of six-nation crisis talks had been expected in Beijing this month, but was postponed due to differences over the steps needed for a settlement.

Washington has demanded that Pyongyang unilaterally scrap its nuclear program, while North Korea has insisted on a legally binding security guarantee from the United States in return for a nuclear climb-down.

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