Rice will also visit China and Japan to try to make progress on the six-nation disarmament deal, which is currently bogged down by disagreements over a promised North Korea nuclear declaration.

Rice made no statement either on the plane or after landing, according to an AFP reporter travelling with her.

In Seoul, Rice will attend Monday's inauguration of President Lee Myung-Bak and will hold talks with him, outgoing Foreign Minister Song Min-Soon and Song's designated successor Yu Myung-Hwan.

Under the accord, the North was supposed to have disabled its main plutonium-producing atomic plants and to have declared all nuclear programmes by last December.

Disablement is going ahead, but the declaration is being held up by disagreements over what it should include.

The United States says the communist state must fully answer suspicions that it bought equipment for a covert uranium enrichment bomb-making programme. The North denies such a programme, and says the equipment was purchased for other purposes.

Rice said Friday that North Korea should not only disclose its nuclear weapons programmes.

"We need a complete declaration from the North Koreans about both their proliferation activities, their current plutonium programme -- which they are in the process of disabling, but also the HEU (highly enriched uranium) programme, that they need to make clear what has happened there," she said.

Washington demands North Korea clear up suspicions of possible nuclear technology transfer to Syria. Media reports have said an Israeli air strike in Syria last September may have targeted a joint nuclear project.

Christopher Hill, Rice's chief negotiator, said that during talks last week in China with his North Korean counterpart Kim Kye-gwan, they "discussed all the elements that we believe need to be included (in the declaration), including the Syrian matter and uranium enrichment."

The six-party talks, which began in 2003, group the two Koreas, the United States, China, Russia and Japan.

Under a deal reached in February 2007, the North was to receive one million tonnes of fuel oil or equivalent energy aid in return for disablement and a declaration.

The aid has been only partially delivered. The North also complains that Washington is dragging its feet on a pledge to start the process to remove it from a list of state sponsors of terrorism.

South Korea's new president Lee has promised a firmer line with North Korea, which staged a nuclear test in October 2006, linking Seoul's aid more closely to disarmament.

Robert Einhorn, a former US government non-proliferation chief who worked on the North Korean nuclear issue, doubted there would be any breakthroughs during Rice's trip, because she had no plans to meet the North Koreans.

But he expected her visit here would boost diplomatic efforts.

"Over the last six or so years, the US and the ROK (Republic of Korea) have not been singing from the same song book on dealing with North Korea," Einhorn told AFP last week in Washington.

"I think with this new South Korean government, the US and South Korea will be much closer together and hopefully will be able to push through a much more coherent and purposeful policy," Einhorn said.

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