Seoul is preparing to ask the UN Security Council to censure North Korea over the sinking a South Korean warship, a diplomat said Thursday.

The diplomat, who spoke on condition of anonymity, said visiting South Korean Vice Foreign Minister Chun Young-woo would make the formal request for a censure resolution soon.

He said Chun would ask the 15-member council to condemn Pyongyang after a multinational investigation concluded last month that a North Korean submarine torpedoed South Korea's Cheonan corvette in March with the loss of 46 lives.

But the diplomat said Chun, who met with several council ambassadors Wednesday and Thursday, would not press for sanctions to be slapped on the reclusive Stalinist state over one of the worst military attacks since the 1950-53 Korean war.

Seoul has announced a series of reprisals, including cutting off trade with its communist neighbor.

Pyongyang has denied any role in the sinking and has responded to the reprisals with threats of war, sharply raising tensions in the region.

Chun, who held talks with US officials in Washington earlier this week, huddled with UN chief Ban Ki-moon, a fellow South Korean, Thursday to discuss the sinking and brief him on his talks with Mexican Ambassador Claude Heller, the current chair of the Security Council.

South Korea can count on the full support from the United States, Japan and other Western powers, but to secure adoption of the censure resolution, it must also enlist the backing of veto-wielding council members Russia and China, traditionally close allies of Pyongyang.

Russia, which has said it needs "100 percent proof" of the North's involvement, on Monday sent a team of naval experts on a week-long mission to South Korea to review findings of the multinational probe, inspect the wreckage and visit the site of the sinking.

The South Koreans have also asked China to send its own experts but Beijing has not responded, according to local media, some of which said the offer had been rejected.

At a three-way weekend summit, China's Premier Wen Jiabao resisted pressure from the Japanese and South Korean leaders to publicly support the UN move or to condemn the North.

Wen instead called for efforts to ease regional tensions.