NEW YORK — U.S. Secretary of Defense Leon Panetta said it would take Iran approximately one year to build a nuclear bomb.

“The consensus is that if they decided to do it, it would probably take them about a year to be able to produce a bomb and then possibly another one to two years in order to put it on a deliverable vehicle of some sort in order to deliver that weapon,” Panetta said in an interview that aired Sunday on the CBS show “60 Minutes.”

Panetta said the U.S. would take “whatever steps are necessary” to prevent Iran from developing a nuclear weapon, calling it a “red line” for both Israelis and the United States. Asked about the possibility of U.S. military action, Panetta responded that “there are no options that are off the table.”

Meanwhile, Iran offered to extend a visit by nuclear inspectors.

Ali Akbar Salehi was quoted by various media on Monday as saying that he was “optimistic” about the results of the visit this week by inspectors from the U.N.’s nuclear watchdog, the International Atomic Energy Agency, and that their three-day visit could be extended “if necessary.”

The inspectors arrived Sunday as tensions between Iran and the West are ratcheting up.

U.S.-led sanctions have intensified in the wake of an IAEA report in November that cited what it said was strong evidence of a nuclear weapons program, which Iran denies.

Iran has issued and then withdrawn threats to shut the Strait of Hormuz, through which much of the world’s oil must pass.

The United States has increased its naval presence in the region, and the Washington Post reported last week that the Pentagon is considering deploying a floating base for commando raids.