China would be responsible if diplomatic solutions fail in dealing with Iran's nuclear ambitions, the US ambassador to the United Nations warned Thursday, saying Washington expects and will seek Beijing's cooperation for new sanctions. The warning by Zalmay Khalilzad to China and others opposing new sanctions against Iran came shortly after the release of a much-anticipated International Atomic Energy Agency report that found Tehran was generally truthful about its nuclear history, but continued to defy the UN Security Council's demand to halt uranium enrichment. "There has been dragging of feet by the Chinese" on a new council resolution, Khalilzad told reporters. "I don't think that China would want to be in a position to cause the failure of diplomacy to deal with this issue." "I think it's in everyone's interest for this world-defining issue to be resolved diplomatically," he said.