Police block protesters trying to march toward the presidential Blue House in Seoul after a candle-light vigil June 7, 2008.(Xinhua/Reuters Photo) 

In a separate mission, senior South Korean Presidential Secretary Kim Byung-kook was also to leave for the United States as early as Monday to discuss follow-up measures on Lee's phone talks with US President George W. Bush.

During a 20-minute phone conversation with Lee last Saturday, Bush promised to help ease fears of the South Korean public over beef imports, South Korean officials said.

Bush reportedly also pledged to ensure that the United States would not export beef from cattle older than 30 months.

In spite of the assurance from Bush, US legislators have said they will not ratify a sweeping free trade agreement until after the South Korean beef market is opened up.

Analysts say this precondition leaves Lee's administration in a dilemma and to find a solution that can satisfy the South Korean public is no easy job.

(Xinhua News Agency June 10, 2008)