File photo of White House.
The White House has asked the Pentagon to revise a report on how the military would close Guantanamo Bay and transfer inmates to the United States, a US official said Thursday.
Military officials last week said the controversial prison's closure plan would be published "soon," but the White House was unhappy with the document and told the Pentagon to find more ways of lowering costs.
"The president had more questions" about what the Pentagon submitted and "there were things that he didn't like," a US official told AFP, speaking on condition of anonymity.
"He's asking for ways in which in we can reduce the cost."
Since taking office in 2009, Obama has been pushing for the closure of the facility on a US Naval base in Cuba, but lawmakers have repeatedly thwarted him.
On Thursday, he vowed to press ahead with efforts to close Guantanamo, saying the number of inmates may soon be lower than 100. Currently, there are 107.
The official said last week's attacks in Paris had changed the political climate, casting further doubt on when the report would be published.
"Before the attacks, I would have said December, (but) now I don't know," the official said.
The Pentagon this year sent a team of experts to review US sites that could house dozens of the most dangerous detainees following the closure of the prison.
Those sites include the Naval Consolidated Brig in Charleston, South Carolina; Fort Leavenworth in Kansas and a federal prison complex in Colorado. The Pentagon also considered a state prison in Colorado.
Guantanamo costs US taxpayers around $400-450 million annually, according to estimates.
"The administration continues to work diligently on completing the plan to safely and responsibly close the detention facility at Guantanamo Bay," said Commander Gary Ross, a Defense Department spokesman.
"We are currently working to refine additional cost estimates for different aspects of detainee operations. While we don't have a specific timeline, the plan will be delivered to Congress as soon as it is complete."
Guantanamo Bay was opened in January 2002 under the administration of then-president George W Bush to deal with prisoners who were termed "enemy combatants" and denied many US legal rights in the wake of the September 11, 2001 attacks.