"There's no reason for people to think that the president is about to attack Iran. I think that we need to make that clear," White House press secretary Dana Perino said at a briefing.

"He doesn't want people to fear that, because what he is doing is pursuing a diplomatic track," Perino said.

The United States has sharply toughened its rhetoric on Iran recently, triggering concerns that the United States might launch military strikes against Iran.

Washington has accused Iran of trying to develop nuclear weapons under the cover of a civilian nuclear program. Iran has denied U.S. charges and insisted that its nuclear program is for peaceful purposes only.