WASHINGTON — 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.

The slow pace is the result of the law that gives Defense Secretary Chuck Hagel — not the commander in chief — the final authority to transfer any of the 149 terror suspects being held at Guantanamo. Pentagon officials said they must carefully consider the risks before signing off, given that others have returned to terrorism.

The White House has reminded the Pentagon that recidivism risks must be weighed against the danger to the United States in keeping the Cuban prison open. Obama has said Guantanamo’s continued operation hurts U.S. standing overseas and is a recruitment tool for terrorists.

“The president would absolutely like to see more progress in our efforts to close Guantanamo,” Obama counterterrorism adviser Lisa Monaco said. “He wants it closed. He’s pushing his own team very hard, raising it weekly with me, with Secretary Hagel, with Secretary (of State John) Kerry. He also wants Congress to act to remove the restrictions in place that are making it even harder to move forward.”