North Korea probably would not use nuclear weapons against US forces unless Pyongyang thought it was on the verge of "military defeat and risked an irretrievable loss of control," US President Barack Obama's top intelligence official said Thursday. National Intelligence Director Dennis Blair told lawmakers Thursday that North Korea probably views its nuclear weapons as being more for deterrence, prestige and "coercive diplomacy" than for fighting wars. He also noted "increasing concerns" among some in the intelligence community that North Korea is secretly enriching uranium. Media have reported the North Koreans were moving to a launch pad a suspected long-range missile capable of reaching the western United States. Also, 28,500 US troops are in South Korea.