The CIA assessment appeared to dispute earlier reports by the U.S. intelligence community. Until early 2010, the agency stuck by a National Intelligence Estimate released in 2007 that asserted that Iran would be unable to produce nuclear warheads until as late as 2015.

Still, Panetta said the CIA continues to disagree with the Israeli assessment on Iranian progress toward a nuclear weapon. He said Iran has been hampered in its uranium enrichment program but would not say whether this was linked to reported CIA sabotage.

"I can’t speak to, obviously, intelligence operations, and I won't," Panetta said. "It’s enough to say that clearly, they have had problems."

Panetta, in an assertion that appeared to dispute the administration of President Barack Obama, also dismissed the effectiveness of the new United Nations Security Council sanctions on Iran. He said the sanctions would probably not halt Iran's nuclear weapons program.

"Will it deter them from their ambitions with regards to nuclear capability?" Panetta said. Probably not."

In an interview on U.S. television, Panetta said Iran would need a year to develop nuclear weapons and another year for a delivery system. He did not elaborate.

"We would estimate that if they made that decision, it would probably take a year to get there, probably another year to develop the kind of weapon delivery system in order to make that viable." Panetta said.

Iran has been developing an arsenal of liquid- and solid-fuel intermediate-range missiles. Officials said both the operational liquid-fuel Shihab-3 and the new solid-fuel Ashoura were designed to contain nuclear warheads.

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