The newly-appointed US diplomat to multinational talks on the North Korean nuclear crisis, Christopher Hill, and South Korea's chief negotiator, Deputy Foreign Minister Song Min-Soon, both arrived from Seoul.

The visits come one week after North Korea declared publicly that it possesses nuclear weapons and was suspending participation in the dialogue.

In Washington, the CIA said the unpredictable state could resume missile tests soon and has active biological and chemical weapons programs.

"North Korea could resume flight testing at any time ... including longer-range missiles capable of reaching the United States," CIA Director Porter Goss testified at a Senate Intelligence Committee hearing in Washington.

"We believe North Korea has active CW (chemical weapons) and BW (biological weapons) programs ... ready for use."

Goss did not say whether North Korea's nuclear technology would allow it to launch a nuclear-tipped missile.

In 1998 North Korea launched a long-range ballistic test missile over key US ally Japan, prompting Japan to begin researching missile defence.

In a phone conversation with Chinese counterpart Li Zhaoxing, Japanese Foreign Minister Nobutaka Machimura Wednesday made it clear that Tokyo would not tolerate a nuclear-armed North Korea.

The discussions in Beijing precede an expected weekend visit to the North by a special envoy from China, the broker and host of the six-nation talks and North Korea's closest ally.

"The point of his visit was to get to know his counterparts and get the six-party talks process moving forward," the US embassy said of Hill's talks with China's pointman on North Korea Wu Dawei and Foreign Minister Li.

Hill and Song did not meet formally and there were no trilateral talks, the embassy said.

The United States, Japan and South Korea -- who along with Russia, China and North Korea are the participants in the six-nation talks -- believe Beijing's influence over Pyongyang is vital to bringing it back to the negotiating table.

China is dispatching Wang Jiarui, the head of the Chinese Communist Party's International Liaison Department, to Pyongyang "this week", the foreign ministry said. It is widely believed he will leave on Saturday.

The ministry refused to comment Thursday on the North's announcement that it is nuclear-armed, but called for patience and reiterated that China favoured a nuclear weapons-free Korean peninsula.

"Our position in this regard is consistent," said spokesman Kong Quan.

The flurry of diplomacy follows telephone discussions between most of the key players, including between the foreign ministers of Russia and North Korea.

Both sides Wednesday "spoke out in favor of a rapid resumption of the six-way negotiating process", the Russian foreign ministry said in a statement.

Japan's Machimura spoke Thursday with his South Korean counterpart Ban Ki-Moon as part of efforts to re-start the talks.

Machimura and Ban said they would try to find a date late next week for the US, Japanese and South Korean negotiators to meet in Seoul, the Japanese foreign ministry said.

Machimura heads to Washington for talks Saturday with US Secretary of State Condoleezza Rice on North Korea and other issues.

The last round of six-party talks was in Beijing in June last year. North Korea shunned a fourth round set for last September, complaining of "hostile" US policies.

The United States and North Korea have been locked in a stand-off since October 2002 when Washington accused Pyongyang of operating a secret program based on highly-enriched uranium, violating a 1994 arms control agreement.

North Korea denied the allegations. However it responded by expelling UN nuclear inspectors, restarting a mothballed nuclear reactor and extracting weapons-grade plutonium from spent fuel rods.

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