The US will have about a year to respond to Iran should the Islamic Republic decide to build a nuclear weapon, US Secretary of Defense Leon Panetta said Tuesday.

“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 [Iran],” Panetta said on CBS’s This Morning.

His words came on the heels of a tiff between the US and Israel over the setting of red lines for Iran, beyond which military action would be taken against it.

Prime Minister Benjamin Netanyahu has called for a clear declaration, and on Tuesday struck back at the US for rebuffing the calls, saying Washington had no right to hold Israel back from taking action while refusing to give assurances.

Panetta said on Tuesday that the US keeps good track of Tehran’s program and would know if the Iranians broke out toward a bomb.

“We know generally what they’re up to. And so we keep a close track on them,” he said. “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.”

On Tuesday, diplomats told the Associated Press that Iran had advanced its work on calculating the destructive power of an atomic warhead through a series of computer models that it ran sometime within the past three years.

The diplomats said the information comes from Israel, the United States and at least two other Western countries and concludes that the work was done sometime within the past three years. The time-frame is significant because if the International Atomic Energy Agency decides that the intelligence is credible, it would strengthen its concerns that Iran has continued weapons work into the recent past — and may be continuing to do so.

Israeli and the US officials have said in the past that the countries agree on the seriousness of the threat a nuclear Iran poses but have different timetables regarding how they see the program advancing and when military action must be taken.

Iran, for its part, maintains its program is peaceful.