Iran will not be allowed to develop nuclear weapons, U.S. Defense Secretary Leon Panetta told CBS News on Monday, adding that despite efforts to spoil Iran's nuclear program the country has already progressed enough to assemble a bomb within a year or less.

Panetta also said the timeline for Iran perhaps building a bomb faster could be different if Tehran had a secret hidden site. But a Pentagon spokesman on Tuesday tried to play down Panetta's comments, saying he was speaking hypothetically and was not suggesting that new intelligence has found secret facilities.

In the interview with CBS News, Panetta also refused to rule out military action to prevent Iran from obtaining nuclear weapons.

If they proceed and we get intelligence that they're proceeding in developing a nuclear weapon, then we will take whatever steps are necessary to stop it, Panetta said. The United States does not want Iran to develop a nuclear weapon. That's a red line for us and that's a red line, obviously, for the Israelis. If we have to do it we will deal with it.

Panetta's remarks raised eyebrows among weapons experts who track Iran's program, particularly his reference to the possibility of a secret facility, the AFP reported.

It's definitely misleading, said David Albright, president of the Washington-based Institute for Science and International Security. The likelihood that Iran could have a nuclear weapon within a year was a low probability as any shift to weapons-grade uranium would be exposed by inspectors and Israel would almost certainly take military action, he said, AFP wrote.