Officials said the detainee, whom they declined to identify, was being interrogated by American officials at a temporary detention facility in the city of Erbil in northern Iraq. They said the plan was to eventually turn him over to Iraqi or Kurdish officials.

Several Defense Department officials declined to say how much information or cooperation they have received from the detainee. They said it could take weeks or months to finish questioning the operative.

As is protocol, Defense Department officials notified the International Committee of the Red Cross, which monitors the treatment of detainees, that they were holding an Islamic State fighter. A Red Cross spokesman, Trevor Keck, declined to comment on the matter, including on whether Red Cross personnel were observing the detainee’s treatment at the facility in Erbil.

Defense Department officials said that the United States had no plans to hold the detainee or others indefinitely, and that they would be handed over to Iraqi or Kurdish authorities after they have been interviewed.