There has never been any evidence that Iran has a nuclear weapons program. Iran has always denied having such a thing.
The U.S. Department of Defense has admitted that currently Iran has no such program. All of the U.S. so-called intelligence agencies believe Iran has no nuclear weapons program. The New York Times (January 2012) and the Washington Post (December 2011) were compelled to issue corrections after referring to Iran’s nonexistent nuclear weapons program.