State Department spokesman Mark Toner said that the UN watchdog had confirmed Washington's long-standing allegation that Tehran had once been working on a nuclear bomb, but he added that Iran had cooperated adequately with IAEA investigators.
"The IAEA report is consistent with what the United States has long assessed with high confidence," Toner told reporters.
"We made this public first in our 2007 National Intelligence Estimate, and that is that Iran had a nuclear weapons program that was halted in 2003."
But, Toner said, now that the IAEA had been able to study the program and had found no evidence that it had continued beyond 2009, the United States was ready to move ahead.
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"The IAEA has confirmed that Iran met its commitments to provide responses to IAEA requests under the roadmap for clarification of past and present issues," he said.
Washington and the other members of the P5+1 contact group -- Britain, China, France and Russia, plus Germany -- will submit a motion to the IAEA board on December 15 to close the issue of what has been called the "possible military dimensions" of Iran's program.
"And then, after that, we can focus on implementing the JCPOA," Toner said, referring to the Joint Comprehensive Plan of Action agreed between Iran and the P5+1 powers in July.
Under the deal, Iran will scale back its nuclear enrichment program dramatically -- a program it has always maintained was for purely peaceful purposes -- and submit its nuclear sites to international inspection.
In return, outside powers will end some of the international sanctions that have severely squeezed the Iranian economy.