The departure of Li Changchun, a member of the Chinese Communist Party's powerful nine-strong standing committee, marked a new drive in the quest to prevent the talks from derailing.

In Tokyo, the senior delegates to the North Korean talks from Japan, South Korea and the United States were meeting to swap notes.

British Foreign Office minister Bill Rammell, meanwhile, was preparing to leave London as the first British minister to visit North Korea.

Li, who runs China's extensive propaganda network, was accompanied on the "goodwill" visit by vice foreign minister Wu Dawei and the party's leading foreign affairs official Ji Bingxuan, Chinese officials told AFP.

He is expected to meet Stalinist leader Kim Jong-Il and also discuss South Korea's explosive admission that it has a covert nuclear enrichment program, an issue that has worked to complicate the North Korean issue.

It is the highest-level Chinese visit to North Korea since hermit leader Kim travelled to China, a close ally, in April.

The previous round of multinational talks in June, that also include South Korea, Russia, Japan and the United States, ended without concrete results, other than agreement to meet again in Beijing by the end of September.

But since then North Korea has adopted a more strident tone toward the United States and South Korea and has expressed doubt about the value of attending further discussions.

In recent days Seoul's admission that South Korean scientists carried out an unauthorised experiment to enrich uranium and plutonium has complicated matters, with North Korea warning of an arms race in Northeast Asia.

Beijing Thursday urged restraint from all sides "in this difficult moment", while expressing hopes the six-party process, that have been largely brokered by China, could be pushed forward.

"We hope that, in this difficult moment, the relevant parties will display patience and restraint and pragmatism and jointly push for the fourth round of six-party talks to be held before the end of September, as we agreed earlier," said foreign ministry spokesman Kong Quan said.

With signs that the talks are in danger of collapsing, Foreign Office minister Bill Rammell was leaving London to try and persuade Pyongyang to ditch its nuclear weapons program.

Britain wants to see North Korea follow the example of Libya, which is abandoning its program for weapons of mass destruction after secret talks with London and Washington.

"North Korea has a key choice," said Rammell, who plans to hold talks with North Korean Foreign Minister Paek Nam Sun and other senior figures.

"It can engage in this process and get rid of what it has got and promise not to develop anything further ... then all sorts of positives can come its way. Isolation is the alternative route."

Rammell admitted though that "this is the start of a very, very long haul to try to edge North Korea back from complete isolation".

Britain, which suspects North Korea has one or two nuclear weapons, established diplomatic relations with the reclusive state in December 2000.

The stand-off flared in October 2002 when the United States accused Pyongyang of operating a nuclear weapons program based on enriched uranium, violating a 1994 agreement.

Pyongyang has denied running the uranium-based program but has restarted its plutonium program.

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