The US stopped just short of disputing North Korea's assertion that it shared information on its nuclear program two months ago. White House spokesman Tony Fratto said, “What we're looking for is a formal, official declaration." Another administration official played down the North Korean assertion, saying it followed a pattern of public posturing in advance of new talks. Chief American negotiator, Assistant Secretary of State Christopher Hill, left Washington Friday en route to China, where the status of North Korea’s adherence to its commitments to dismantle its nuclear weapons program will be the focus of a new round of negotiations.