South Korean President Lee Myung Bak left for the United States Monday for talks on the increasingly critical nuclear dispute with North Korea, as media in Seoul reported that North Korea could have built several underground nuclear test sites, dpa reported. Meanwhile, International Atomic Energy Agency (IAEA) chief Mohamed ElBaradei said in Vienna he was "greatly concerned" about North Korea's recent atomic test, which had created an environment of confrontation. Lee is due to meet US President Barack Obama on Tuesday in Washington to discuss ways to cooperate "to achieve the complete and verifiable denuclearization of North Korea," an official from Lee's office in Seoul said. North Korea's launch of a long-range rocket in April and its second nuclear test on 25 May have significantly raised tensions on the Korean peninsula and in the region. Lee wants written reassurance from the US that South Korea is protected by its "nuclear umbrella," an official from the President's Office told the national news agency Yonhap. However, South Korea fears its northern neighbour could conduct a third test in reaction to sanctions passed by the United Nations Security Council on Friday. So far, Pyongyang has responded by threatening war and announcing it would build more nuclear weapons. A statement from Pyongyang said it was in the "early phase of an open-ended confrontation with the US." Referring to the blast on May 25, ElBaradei said: "I deeply regret this, particularly at a time when the prospects for progress on nuclear disarmament are far better than they have been at any time in the recent past." US President Barack Obama has vowed to push ahead with nuclear disarmament, including through arms reduction talks with Russia and efforts to ratify the Comprehensive Nuclear-Test-Ban Treaty.
