South Korea's nuclear envoy left for Russia on Wednesday to review efforts to restart long-stalled regional talks on North Korea's nuclear disarmament, the foreign ministry said.
Lim Sung-Nam's visit came a day after the United States held what were termed "very positive" talks with the North in Geneva on reviving the six-party forum.
"At this time when two rounds of inter-Korean and North Korea-US meetings have been wrapped up, we will review the progress and discuss future moves," Lim told Yonhap news agency.
He will meet his Russian counterpart Alexei Borodavkin and other senior officials during the three-day visit.
The first US-North Korea talks were held in New York in July and the two Koreas met in July and September as part of efforts to reopen the multilateral nuclear dialogue.
Stephen Bosworth, the outgoing US special envoy on North Korea, Tuesday described the Geneva talks as "very positive and generally constructive" but cautioned that not all differences could be quickly overcome.
North Korea's chief delegate, first vice minister Kim Kye-Gwan, said "big progress" had been made and the two sides had agreed to meet again.
But US State Department spokeswoman Victoria Nuland downplayed the results, saying "while there's been some narrowing of differences, we haven't had any breakthroughs here and significant issues do remain".
The North formally quit the six-party forum in April 2009, a month before staging its second atomic weapons test.
It has since repeatedly said it wants to come back without preconditions to the negotiations, which group the two Koreas, the US, China, Russia and Japan.
Washington and its allies say Pyongyang must first take action to show its sincerity, such as shutting down a uranium enrichment plant that could be converted to make nuclear weapons.
China's vice premier Li Keqiang was due in South Korea Wednesday following a visit to the North and talks with leader Kim Jong-Il.
Kim reportedly said he wants the six-party talks to resume as soon as possible based on the "principle of simultaneous action" -- a reiteration of the North's stance that the negotiations restart without preconditions.