The United States would have about a year to take action if Iran decided to build nuclear weapons and the American military is well-prepared if the moment comes, Defense Secretary Leon Panetta said in a television interview Tuesday.
The Pentagon chief told "CBS This Morning" that it would take Iran some time to construct a nuclear device once the Tehran leadership chose to go ahead.
"It's going to take them a while once they make the decision to do it," he said.
Asked how much time it would take, Panetta replied: "It's roughly about a year right now. A little more than a year.
"And so, we think we will have the opportunity once we know that they've made that decision, take the action necessary to stop (the program)."
Panetta's comments come amid tension with Iran over its nuclear program as well as growing friction between the United States and Israel over the urgency of the threat posed by Tehran's uranium enrichment work.
Israeli leaders have portrayed Iran as on the verge of securing nuclear weapons and warned US officials that a "zone of immunity" could soon emerge in which it would be too late to stage bombing raids to derail Tehran's program.
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President Barack Obama's administration has taken a more cautious approach, suggesting there is still time to allow sanctions to take effect and for more potential sabotage of Iran's nuclear sites, according to analysts and former officials.
Panetta said US spy agencies are able to track Iran's nuclear project and assess how close the Islamic republic may be towards achieving the capability to build an atomic bomb.
"We have pretty good intelligence on them. We know generally what they're up to. And so we keep a close track on them," he said.
Panetta declined to discuss bunker-busting bombs in the US arsenal designed to penetrate underground facilities that could house centrifuges in Iran, but he said the American military had the means to prevent Tehran from getting its hands on the bomb.
"Without going into what particular capabilities we have, we think we've got the ability to be able to strike at them effectively, if we have to."
He added: "We have the forces in place to be able to not only defend ourselves, but to do what we have to do to try to stop them from developing nuclear weapons."
Experts disagree about how quickly Iran could develop a nuclear threat, including how much time the regime needs to secure a sufficient supply of weapons-grade uranium and then to build and test a weapon.
Iran insists its nuclear program is purely peaceful, for civilian energy purposes.