Ning Fukai, who was appointed last month as special ambassador to coordinate the stalled negotiations, will leave in the coming days, the Chinese foreign ministry told AFP.

He will be accompanied by Fu Ying, director of the Asian section of the foreign ministry.

The decision came as the North Korean foreign ministry snubbed US Secretary of State Colin Powell's suggestion last month that Pyongyang should "get smart" and follow Libya's example.

"This is nothing but a folly of imbeciles utterly ignorant of the DPRK's (North Korea's) independent policy," Pyongyang's official media quoted a foreign ministry spokesman as saying.

Libyan leader Moamer Kadhafi stunned the world last month when he said Tripoli would renounce its quest for chemical, biological and nuclear weapons and welcome international inspections.

"To expect any 'change' from the DPRK stand is as foolish as expecting a shower from clear sky," the North Korean official was quoted as saying.

China, North Korea's closest ally and chief aid donor, has been trying to convene a second round of six-party talks -- also including Russia, Japan and South Korea -- on the 15-month crisis which were tentatively scheduled for December but never went ahead.

The trip to Washington comes after North Korea this week offered to refrain from testing and producing nuclear weapons in what it said was a "bold concession" to the United States.

In return North Korea said it wanted concessions from Washington including an end to sanctions and aid.

Powell responded by saying the chances of a second round of talks on Pyongyang's nuclear ambitions were improving, but signalled that US policy was unchanged.

"They will have discussions with the American side on working issues and will exchange views with the American side on the second round of six-party talks," the Chinese foreign ministry said of Ning's mission.

Two US delegations meanwhile are due back in Beijing Saturday after a five-day trip to North Korea. They hoped to visit the Yongbyon facility where North Korea has said it was reprocessing spent nuclear fuel rods in an effort to make atomic bombs.

"So far the visit has been good, but beyond that I'm not going to comment," US congressional staffer Frank Jannuzi told AFP from his Pyongyang hotel.

Other delegation members also refused to comment.

Jannuzi was travelling with his colleague Keith Luse. Both work for the US Senate Foreign Relations Committee.

The second delegation is led by Stanford University scholar John Lewis and includes former State Department official Jack Pritchard and Sig Hecker, a nuclear scientist who from 1985-1997 directed the Los Alamos National Laboratory, where the atomic bomb was first developed.

Western diplomats in Pyongyang told AFP the teams had kept a low profile in the Stalinist nation. They said the delegations had been "in the field" Thursday.

North Korea agreed in 1994 to mothball its Yongbyon nuclear complex, 90 kilometres (50 miles) north of Pyongyang, under a nuclear freeze agreement with the United States.

But it fired up the facilities while accusing the administration of US President George W. Bush of seeking to scrap the 1994 accord.

Reprocessing Yongbyon's spent fuel rods -- thought to be enough for around six nuclear weapons -- could increase a nuclear stockpile that US intelligence services believes already numbers up to two nuclear devices.

burs/mp/br

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