Two armed drones on Tuesday targeted Iraq's Ain al-Asad airbase, which hosts U.S forces and other international forces in western Iraq, two Iraqi military sources told Reuters.
It was the first attack against U.S. forces in Iraq since early February when Iranian-backed groups in Iraq stopped their attacks against U.S. troops.
No casualties have been reported, said the sources.
An Iraqi military official said defence systems downed one drone near the base perimeter.
The attack came less than a week before an expected visit by a high level Iraqi military delegation to Washington to continue talks on ending the U.S.-led military coalition in the country.
Washington and Baghdad in January initiated talks to reassess the draw-down of the U.S.-led coalition in Iraq, formed in 2014 to help fight Islamic State after the extremist Sunni Muslim militant group overran large parts of the country.
A U.S. official, speaking on condition of anonymity, said a projectile appears to have targeted the base, but without causing casualties.
Reporting by Ahmed Rasheed