However, with the first phase of the fifth round scheduled to last just three days before resuming later in the year, expectations were low that major progress will be made this week.

Progress would be "rather difficult" because large differences remain over how to implement an agreement reached at the last round in September, Chinese vice foreign minister Wu Dawei told journalists.

China, the two Koreas, the United States, Russia and Japan agreed in September to verifiably scrap North Korea's nuclear programs in exchange for energy assistance and other benefits.

However, the United States has insisted that North Korea dismantle its nuclear program immediately, while the Stalinist state has been holding out for benefits from Washington up front before surrendering its bargaining chip.

In particular, North Korea said after the September agreement that it would not dismantle its nuclear arsenal before the United States supplied it with a light-water atomic reactor to generate electricity.

The United States says North Korea must first disarm.

Japan's chief negotiator, Kenichiro Sasae, told reporters after arriving in Beijing on Tuesday that North Korea would be urged to adopt a phased approach to dismantling its nuclear weapons program.

"We will study how to implement what we agreed at the last six-party round," Sasae said. "We believe it is necessary to achieve progress on the central question, that is how to proceed in concrete terms with nuclear disarmament, which was promised by North Korea.

"Japan for its part believes it is important to present a specific prospect leading to next steps."

Sasae did not give details, but the Japanese Asahi Shimbun newspaper said Japan, the United States and South Korea would propose to the North a "road map" under which it would give up its nuclear weapons in return for promised benefits.

The road map would include a timeline for ways for Pyongyang to verify it is giving up its nuclear program, the Asahi Shimbun said, citing South Korean diplomatic sources.

The newspaper said the road map would include a series of stages starting with North Korea confirming its nuclear programs are dismantled, freezing nuclear facilities and renouncing its nuclear program.

In exchange for further benefits, Pyongyang would eventually need to return to the Nuclear Non-Proliferation Treaty (NPT) and accept inspections by the UN International Atomic Energy Agency.

The United States and Japan accuse North Korea of violating a 1994 agreement under which a US-led consortium would have built two light water reactors in the impoverished state in return for nuclear disarmament.

The United States accused the North in 2002 of developing a secret uranium-enrichment program. The North responded by throwing out weapons inspectors and leaving the NPT.

All the delegations to the talks, except the US team led by Christopher Hill, had arrived in Beijing by mid-afternoon on Tuesday. Hill was due to land in the early evening.

The other delegations were holding various bilateral meetings on Tuesday.

The chief negotiators for both Koreas met for about 100 minutes on Tuesday but said little to reporters afterwards.

"We have had constructive and in-depth talks about how to implement the joint statement," North Korean lead delegate Kim Gye-gwan said.

North Korea will enter the talks in a familiarly angry mood, with a North Korean foreign ministry spokesman saying on Tuesday that US President George W. Bush had on this week's trip to Brazil slandered leader Kim Jong-Il.

Bush "malignantly slandered our supreme headquarters with such unspeakable vituperation as 'tyrant' and the like," the spokesman said in a statement carried by the North's official Korean Central News Agency.

"If this is true, what he uttered is a blatant violation of the spirit of the joint statement of the six-party talks which calls for 'respect for sovereignty' and 'peaceful co-existence'."

Russia's Interfax news agency quoted a North Korean official as restating Pyongyang's position that it wanted a nuclear reactor, diplomatic relations with the United States and other assistance to coincide with it disarming.

China has asked that the first phase of the next round of talks ends by Friday so that diplomats can also attend the Asia Pacific Economic Cooperation summit in South Korea on November 18 and 19.

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