US envoy Christopher Hill, who leads Washington's team to the six-way talks, left for Tokyo on a two-day mission focusing on how to coax Pyongyang back to dialogue, the US embassy said.

South Korea's chief nuclear negotiator and Deputy Foreign Minister Song Min-Soon departed for Moscow on a five-day mission with a similar agenda, officials said.

South Korean Foreign Minister Ban Ki-Moon on Wednesday urged Pyongyang repeatedly to return to talks involving the two Koreas, the United States, China, Russia and Japan.

"It is the most urgent thing that North Korea come back to dialogue," Ban said in a weekly briefing.

The goal of ending North Korea's nuclear weapons drive gained urgency on February 10 when Pyongyang said it had nuclear weapons and withdrew indefinitely from the nuclear negotiations, blaming a "hostile" US policy.

The Stalinist North raised the stakes last Thursday by saying it had ended a self-imposed 1999 moratorium on testing long-range missiles.

"Ambassador Hill will meet with his Japanese counterpart in Tokyo on Thursday," US embassy spokeswoman Maureen Cormack said.

Hill, who was named assistant secretary of state for east Asian and Pacific affairs last week, will then travel to Washington for a confirmation hearing at the US Senate, she said.

Song, who has led South Korea's team to the six-way nuclear talks, is visiting Moscow until Sunday to meet with his Russian counterpart Alexander Alexeyev, according to Seoul's foreign ministry.

Last week, China sent Vice Foreign Minister Wu Dawei, Beijing's chief nuclear negotiator, to Seoul. Wu held a series of meetings with Song and Hill.

Ning Fukui, China's envoy on the Korean peninsula and deputy chief of Beijing's team to the talks, also began his US trip on Tuesday for discussions with US officials.

North Korea has been urged to come back to six-way talks which began in August in 2003 to address the standoff that erupted in 2002 when Washington accused Pyongyang of operating a secret uranium-enrichment program.

The three sets of six-way talks produced little progress with the final round held in June 2004. North Korea boycotted a fourth round, originally due to be held in September last year.

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