A U.S. official told The Associated Press the individual was an American stationed at the Makhmour base outside the Islamic State group-held city of Mosul.
The attack was an “indirect fire attack,” specifically rockets, the official said. The official spoke on condition of anonymity as he wasn’t authorized to brief the media.
Less than five were wounded in the attack, an unnamed official told Fox News.
Two Iraqi commanders stationed at the base also reported a rocket attack Saturday, but denied anyone had been hurt or killed.
The U.S.-led coalition has reported that the build-up of Iraqi troops at Makhmour in preparation for an assault on Mosul has brought a spike in the frequency of such indirect fire attacks.
The last U.S. service member killed in Iraq was in October 2015, when Army Master Sgt Joshua Wheeler became the first American casualty in Iraq since the withdrawal of US forces from Iraq in 2011.
In December, a special task force mission deploying 200 men in a kill/capture mission against ISIS was announced.
There are approximately 3,700 US troops on the ground in Iraq, largely advising the Iraqi army.
The Associated Press contributed to this report.