A U.S. service member who died when an improvised explosive device detonated while he was on patrol outside the northern Iraqi city of Mosul was identified on Sunday as 1st Lt. Weston Lee.

Lee, 25, of Bluffton, Georgia, was an infantry officer assigned to 1st Battalion, 325th Infantry Regiment, 2nd Brigade Combat Team, 82nd Airborne Division, the U.S. Army said in a statement.

U.S.-backed forces have been fighting to retake the Islamic State strongholds of Mosul.

News of the death came as U.S. President Donald Trump marked his first 100 days in office. During last year's presidential election campaign, Trump vowed to give priority to destroying Islamic State, which operates mostly in Syria and Iraq.