USFOR-A said the operation targeting the Islamic State's Khorasan Province branch occurred in Nangarhar's Achin district on Saturday.
"On behalf of all U.S. Forces - Afghanistan, I offer our deepest condolences to the family and friends of our fallen comrade," USFOR-A commander Gen. John W. Nicholson said in a statement. "We will always remember our fallen comrades and commit ourselves to deliver on their sacrifice."
The U.S. Department of Defense said it would withhold the identity of the solider until the notification of next of kin.