WASHINGTON (AP) — The transfer of prisoners out of Guantanamo Bay has ground to a halt amid a slow Pentagon approval process, causing deep frustration within the administration and raising doubts that President Barack Obama will be able to fulfill his campaign promise to close the offshore prison for terrorism suspects.

A detainee sent back to his native Algeria in March is the only prisoner to have moved out this year, beyond the controversial exchange of five Taliban members in return for long-held captive U.S. Army Sgt. Bowe Bergdahl.