The U.S. Treasury Department is imposing sanctions against North Korea's Foreign Trade Bank (FTB), the reclusive nation's main foreign exchange institution, for its role in supporting Pyongyang's nuclear program, President Barack Obama's national security adviser said Monday. Tom Donilon also said in a speech to the Asia Society in New York that China should not conduct "business as usual" with North Korea while Pyongyang threatens its neighbors. "The United States will not accept North Korea as a nuclear state," Donilon said. "Nor will we stand by while it seeks to develop a nuclear-armed missile that can target the United States." Donilon said that Washington is willing to negotiate with North Korea, but he insisted that it must first take "meaningful steps" to meet its international obligations.