The Islamic State group is no longer “on the march,” said CIA Director John Brennan, who argued Sunday the militant organization’s momentum in Iraq and Syria had been blunted by U.S. and Iraqi efforts at fighting the jihadist advance.

"Clearly ISIS's momentum inside of Iraq and Syria has been blunted, and it has been stopped. So they are not on the march as they were several months ago," Brennan said in an interview on "Fox News Sunday." "Our working with the Iraqis, and now the Iraqis trying to push back against it, it is having some great progress."

The U.S. is currently leading a coalition of more than 60 countries dedicated to stamping out the group, with multinational forces carrying out nearly 2,900 airstrikes against ISIS targets in Iraq and Syria, the Pentagon has said. Since the start of the campaign Aug. 8, the U.S.  military alone has flown 2,320 airstrikes against the militants, at a cost of $1.83 million.

While Washington has dedicated significant resources to the fight against ISIS, which seized broad swathes of territory in Iraq and Syria last summer, a top former U.S. official has warned the biggest threat to the region is not the militant group but, rather, the anti-ISIS militias funded by Iran. "Longer term, Iranian-backed [Shiite] militia could emerge as the pre-eminent power in the country, one that is outside the control of the [Iraqi] government and instead answerable to Tehran,” said former CIA Director David Petraeus in an interview with the Washington Post last week.

Iran’s elite Revolutionary Guard is currently on the ground in Iraq and a major force in the ongoing campaign by Iraqi forces and militias against the ISIS stronghold of Tikrit. The Islamic Republic deployed advanced rockets and missiles to the country last week to bolster its efforts in Tikrit, U.S. intelligence agencies said. While Iran and the U.S. are both engaged in the battle against ISIS in Iraq, they have avoided coordinating efforts, with Brennan saying he “wouldn’t consider Iran an ally” in the fight.