Envoy Wi Sung-Lac told reporters his trip would focus on how to cope with the uranium programme in the context of the Security Council.

It would also consider ways to create the right conditions for resuming long-stalled six-party talks on the North's nuclear disarmament, Yonhap news agency quoted him as saying.

Wi will meet his US counterpart Sung Kim and Assistant Secretary of State for East Asia Kurt Campbell during his two-day visit, the foreign ministry said.

He will also hold talks with US special representative on North Korea Stephen Bosworth and officials of the White House National Security Council.

On Wednesday the North's ally China refused to let the UN Security Council publish a report on the North's nuclear sanctions-busting, diplomats said.

The sanctions panel report calls for tougher implementation of the measures and outlines the progress the North has made on uranium enrichment, according to diplomats.

It describes the enrichment as a new violation of sanctions imposed following atomic tests in 2006 and 2009.

China chairs the six-party talks last held in December 2008 and has been trying to revive them to ease overall tensions on the Korean peninsula. It says the uranium issue should be dealt with at that forum.

Chinese Foreign Minister Yang Jiechi called for an early resumption of the talks during his two-day visit to Seoul that began on Wednesday.

South Korean President Lee Myung-bak described Pyongyang's nuclear ambitions as a threat to regional peace and to the world's non-proliferation regime.

Genuine multinational security cooperation was possible in the region only when the "Cold War remnants" were removed from Korea, Lee said in a speech to a a conference in Seoul.

"North Korea's constant attempts to develop nuclear programmes remain a challenge not only to inter-Korean security issues but also peace in Northeast Asia and the world's non-proliferation regime," Lee said.

He called on the North to scrap its nuclear programme and follow China and Vietnam in opening up its command economy, allowing the two Koreas to make peace and build an economic community.