While the release did not provide details regarding the service member's location or cause of death, the head of U.S. Central Command, Gen. Joseph Votel, told reporters on Thursday morning that "initial reports" suggested the service member had been killed from "combat action."
Votel offered his condolences to the service member's family and unit.
"In terms of attributing it to anybody, ISIS or Taliban, I think we'll have to find out more at this particular point," he said.
The identify of the service member will be withheld 24 hours pending next of kin notification.
The incident is under investigation, Resolute Support said.
"We mourn and honor the sacrifice of our service member,” Resolute Support and U.S. Forces Afghanistan Commanding General Scott Miller said in the statement. “We remain committed.”
In September, the U.S. lost two service members in Afghanistan, where there are about 14,000 troops advising and assisting the country's military in its fight against ISIS and the Taliban.
Command Sgt. Maj. Timothy A. Bolyard, 42, from Thornton, West Virginia, was killed on Sept. 3 during an insider attack in Logar Province.
The following day, Staff Sgt. Diobanjo S. Sanagustin, 32, from National City, California, died from a non-combat related injury at Bagram Air Field.
The 17th anniversary of the U.S. war in Afghanistan is this Sunday, Oct. 7.