"I aware that North Korea has expressed its willingness through a third country to discuss the issue of HEU (highly enriched uranium) with the United States," an unnamed top government official here told Yonhap.

"There are signs of changing in North Korea's position."

The comments came one day after a top US envoy John Bolton warned Pyongyang's refusal to discuss its uranium enrichment program could derail the chances of finding a peaceful solution to the standoff.

"I think North Korea's unwillingness to discuss the uranium enrichment program could subvert President (George W.) Bush's determination for a peaceful diplomatic resolution of the North Korean issue," Bolton said Wednesday.

The two Koreas, the United States, China, Russia and Japan will meet in Beijing on February 25 in a second-round bid to resolve the 16-month standoff on Pyongyang's nuclear ambitions.

The first round ended inconclusively in Beijing in August last year.

South Korean Foreign Minister Ban Ki-Moon said Wednesday he hopes to see "visible and positive" progress -- such as a joint statement -- at the fresh round of six-way talks.

The crisis began in October 2002 when the United States said North Korea admitted to having run a secret nuclear weapons program based on enriched uranium in violation of a 1994 nuclear accord.

Pyongyang has denied the claims by Washington, while reactivating its once-frozen nuclear facilities producing weapons-grade plutonium.

Washington wants Pyongyang to abandon all nuclear development, including the alleged enrichment uranium program, in a verifiable and irreversible manner.

But North Korea has only offered to freeze its plutonium-producing facilities if it gets US concessions, including a resumption of energy aid to Pyongyang.

Pyongyang already has one or two crude nuclear bombs made from plutonium diverted from its main nuclear complex at Yongbyon, 90 kilometres (50 miles) north of Pyongyang, before 1994, according to US intelligence.

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