The United States would have about a year to take action if Iran decided to build a nuclear weapon, Defense Secretary Leon Panetta said Tuesday, despite urgent warnings from Israel that time is running out to prevent Tehran from getting the bomb.

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, to 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.

Shortly after Panetta's interview aired, Israeli Prime Minister Benjamin Netanyahu demanded the international community lay down firm "red lines" for Iran in remarks clearly aimed at Washington.

Israeli leaders have portrayed Iran as on the verge of securing nuclear weapons and warned US officials that a "zone of immunity" could take effect in which it would be too late to derail Tehran's program through bombing raids.

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 accurately keep track of Iran's nuclear project.

"We have pretty good intelligence on them. We know generally what they're up to. And so we keep a close track on them," said the former CIA director.

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 warhead, 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, which insists its nuclear program is purely peaceful for civilian energy purposes, has made major strides in uranium enrichment that have dramatically altered previous estimates about Tehran's potential "break-out" to a nuclear weapons capability, analysts say.

The US government once believed that it would take Iran a year to secure enough weapons-grade uranium for a bomb but in the past three years, the Tehran's network of centrifuges has grown from about 4,000 to about 10,000, said David Albright, president of the Institute for Science and International Security and a leading expert on the issue.

Moreover, Iran has amassed a large amount of uranium enriched to 20 percent, while previously the government only had uranium enriched to the much lower level of three-and-a-half percent, he said.

As a result, "you're down to two, three months to make the weapons grade uranium," he told AFP.

That could mean it would take Iran eight to 10 months to obtain a nuclear weapon once it decided to make the move, Albright said.

Panetta's assessment likely will be seen as overly conservative by some in Israel, where Netanyahu urged the world to lay down clear parameters for Iran.

"The world tells Israel: Wait, there's still time. And I say: wait for what? Wait until when?" Netanyahu said.

"Those in the international community who refuse to put red lines before Iran, don't have a moral right to place a red light before Israel," he said.

Underscoring the mounting strain in US-Israeli relations, officials confirmed that Obama and Netanyahu would not meet in New York later this month on the sidelines of the UN General Assembly meeting.

Netanyahu had asked for a meeting but the White House said the president's schedule was too tight to make room for talks with the prime minister.