Iran has reached the point where it can assemble a bomb in a year or potentially less, U.S. Defense Secretary said.

In an interview for CBS's "60 Minutes," Leon Panetta said that should Iran proceed with developing a nuclear weapon "then we will take whatever steps necessary to stop it."

Panetta said Israel's concern for a nuclear Iran is a "common concern" of the U.S., and that Washington would not rule out a military attack.

"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," he said.