In a new interview, CIA Director John Brennan says U.S.-led air strikes and Iraqi government forces have stopped the momentum of Islamic State (IS) fighters in Iraq, while warning Iran against developing nuclear weapons.
Brennan, speaking on the U.S. channel Fox News on March 22, said the Islamic State extremist group is no longer "on the march" -- in both Iraq and Syria -- and "has been stopped."
He said "our working with the Iraqis, and the Iraqis trying to push back against [IS], it is having some great progress."
A U.S.-led coalition has conducted air strikes against IS fighters and strategic targets of the Islamist group since the autumn.
IS militants control large swaths of Iraq and Syria.
Brennan added that despite Iran's help in fighting against IS, he wouldn't "consider Iran an ally" in the battle to defeat the group.
Iranian military advisers and equipment have been used in Iraq in fighting against the IS militants.
Brennan also said the United States can prevent Iran from developing nuclear weapons and that Iranian officials know they will face "tremendous costs and consequences" if they try to develop such weapons.
Brennan said the United States has many ways to ensure Iran doesn't become a nuclear power.
Iran and officials from Britain, Germany, France, China, Russia, and the United States face a March 31 deadline to reach a deal on scaling back Iran's nuclear ambitions in exchange for relief sanctions.
Iran insists its nuclear program is for peaceful purposes.
Brennan said if Iranian officials try to develop nuclear weapons, "they know that they will do so at their peril."
Brennan said U.S. intelligence has a "better plan and opportunity to verify some of the things" the Iranians say they will do.