In a message conveyed by envoy Li Changchun to North Korean leader Kim Jong-Il, Hu said China was willing to work with its neighbour to deepen relations, the Xinhua news agency said.

China also wanted to "strengthen coordination and cooperation in regional and international affairs, with both countries understanding and supporting each other, seeking mutual development and mutual benefit to both peoples", said Hu.

The visit by Li, a member of the Communist Party's powerful nine-strong top committee, is part of last-ditch attempts to persuade Pyongyang to attend a fourth round of six-party talks aimed at resolving the two-year nuclear impasse.

The talks were scheduled to take place before the end of September but Pyongyang has expressed skepticism at their usefulness and questioned the Americans' intentions.

It also hinted that the talks, between the two Koreas, Japan, China, Russia and the United States, could be jeopardised by Seoul's recent admission that South Korean scientists carried out nuclear experiments.

In recent days officials from China, Britain, Russia, Japan and the United States have visited Beijing or Pyongyang.

British foreign office minister Bill Rammell was in the North Korean capital Monday and met Foreign Minister Paek Nam-Sun.

A top Russian official close to President Vladimir Putin met with Kim Monday, ITAR-TASS reported.

US diplomat James Kelly was holding meetings with Chinese officials in Beijing. And South Korea's top nuclear negotiator, Deputy Foreign Minister Lee Soo-Hyuck, left for Russia to enlist Moscow's help in persuading Pyongyang to resume talks.

Amid the flurry of activity, Japanese Foreign Minister Yoriko Kawaguchi expressed cautious optimism the talks could take place this month, saying her hopes were stronger after meeting Chinese officials.

"That is because we know that we all are trying out best," Kawaguchi said in Beijing, adding that it was important to stick to September because "it is what we said we should do".

"Knowing that China is still making efforts ... my hope is strong, is stronger," she said.

China's assistant foreign minister Shen Guofang, however, declined to speculate on whether talks would go ahead this month.

"It's difficult to say right now. We have to coordinate with the other parties," Shen told reporters.

The diplomatic efforts continued as North Korea Monday said a huge explosion that rocked its northern inland province of Ryanggang last week was part of a demolition project to blow up a mountain for a hydro-electric plant.

The blast triggered a mushroom cloud at least three kilometers (two miles) in radius, South Korea's Yonhap news agency said, sparking fears that North Korea may have tested a nuclear device.

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

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