A US diplomat traveled Tuesday to North Korea for talks on the communist nation's efforts to disable its main nuclear reactor. Sung Kim, the US State Department's top Korea expert, crossed into North Korea via the heavily fortified land border with South Korea, the U.S. Embassy in Seoul said. Kim was to stay in North Korea for two days to discuss how it can finish several remaining steps in disabling its Yongbyong reactor as well the possibility of blowing up a cooling tower there, according to the State Department and the embassy. North Korea has promised to provide a complete declaration of its nuclear programs in return for aid and political concessions, but has not yet done so. It handed 18,500 pages of nuclear records to the US in May. The trip comes as the US and South Korea and other nations involved in North Korean nuclear disarmament talks planned to meet in Seoul later Tuesday to discuss details of promised energy aid to the North. A full six-nation meeting on energy aid is scheduled Wednesday at the truce village of Panmunjom, inside the Demilitarized Zone separating the two Koreas.