The trip comes just one day after Lim Sung-Nam was named to the post, replacing Wi Sung-Lac who becomes ambassador to Russia. During his stay until Saturday, Lim and US officials will discuss efforts to revive stalled six-nation negotiations on the North's nuclear disarmament, the ministry said. The talks appeared aimed at coordinating a joint stance before Presidents Lee Myung-Bak and Barack Obama hold a summit in Washington on October 13. The North abandoned the six-party forum in April 2009 and staged its second nuclear test a month later. It is now calling for an unconditional resumption of the negotiations. But the United States and South Korea say the North must first show it is serious about the process, notably by shutting down a uranium enrichment programme which could be reconfigured to make bombs. Last month, the nuclear envoys of South and North Korea held a second meeting in as many months to try to lay the groundwork for the resumption of the six-party talks. No significant progress was reported. US and North Korean officials met separately in New York in late July, and there are media reports that another meeting is planned. The forum also includes China, Russia and Japan.