The Obama administration expects more inmates will be transferred from the Guantanamo Bay military prison this year, a U.S. official said on Thursday, despite the political firestorm over the exchange of five Taliban detainees for the last American soldier held in Afghanistan.

"There are a significant number of transfers in the pipeline at various stages, and I think you are going to be seeing substantial progress this year," a senior administration official, who spoke on condition of anonymity, told a briefing for reporters on moves toward closing the base.

The official declined to say how many of the 149 prisoners still at the U.S. detention center at the naval base in Cuba are up for transfer. Seventy-eight - including 58 Yemenis and four Afghans - have been approved to be released without charge.

The detention camp, much-criticized by human rights groups and others, has been back in the spotlight since Saturday when Sergeant Bowe Bergdahl, 28, was released after being held for five years by the Taliban, in exchange for five Taliban officials held at Guantanamo for 12 years.

News of the swap, which was arranged without consulting Congress, infuriated many lawmakers, particularly Republicans already skeptical about the avowed intention of President Barack Obama, a Democrat, to close the prison.

Oklahoma Senator James Inhofe, the top Republican on the Senate Armed Services Committee, accused Obama of using Bergdahl's release "as an opportunity to pursue his legacy of closing Guantanamo Bay" in a column published at

After being briefed about a potential swap of five prisoners for Bergdahl in late 2011, Congress passed a law, which Obama signed in early 2012, requiring the White House to give them 30 days' notice of any transfers from Guantanamo.

Lawmakers contend that the Bergdahl swap deal violated that law because they were not given notice of the Guantanamo transfers, underscoring the tough fight ahead of the White House as it seeks to shutter the prison.

Advocates for closing the camp say it violates U.S. principles such as not holding prisoners without charge. It also acts as a recruiting tool for anti-American militants, and is very expensive to keep open.

It costs $2.7 million to $2.8 million per year to keep each detainee at Guantanamo, compared with $78,000 per inmate at the highest security prisons in the United States.

Current U.S. law does not allow any prisoners to be moved to the United States from Guantanamo, for trial in federal courts or any other reason, even medical emergency.

Lawmakers who favor closing the base have repeatedly introduced legislation to allow some transfers to the United States. Most recently, they included such provisions in a defense spending bill currently making its way through Congress. Such legislation has repeatedly failed to pass.

(Reporting by Patricia Zengerle; Editing by Grant McCool)