The Islamic State (IS) extremist group has lost nearly half, or 45 percent, of the territory it once held in Iraq, while it has lost nearly a fifth of its territory in Syria, Pentagon spokesman Peter Cook has said.
The 16 to 20 percent of ground lost in Syria compares with an administration estimate of 10 percent earlier this year, while in Iraq the previous estimate was 40 percent.
U.S. and Iraqi forces have repeatedly stressed how IS has gone into retreat in recent weeks, even as the militant group has lashed out with spectacular and deadly attacks on civilian targets in Baghdad and other population centers.
The U.S. military says IS has also lost a significant amount of cash and oil reserves, both of which have been targeted repeatedly by U.S. air strikes.
Since the beginning of the year IS has lost control of Ramadi and Hit, even as it retained control of Fallujah and Iraq's second-largest city, Mosul.
IS made its initial gains in a lightning-fast takeover of large swaths of Iraq and Syria in 2014.