The United States called on Iran to negotiate over its nuclear program, after diplomats agreed to resume talks in two weeks on the subject of Tehran suspending its uranium enrichment. Saturday's talks were the first to include the United States. Just before the talks began, Iran ruled out freezing its enrichment program. In Washington, US State Department spokesman Sean McCormack said Iran has two weeks to "give a clear answer." "Iran has a choice to make: negotiation or further isolation," McCormack said.