LONDON — Britain has asked America to release five British residents detained at the Guantanamo Bay prison camp in Cuba, a shift in strategy on terrorism by Prime Minister Brown.

While Britain persuaded America to hand over its citizens from the military base, it until now had refused to request the release of foreigners who had been legally living in Britain. The British government had fought and won a series of legal battles in defense of its position.

“The foreign secretary and home secretary have reviewed the government’s approach to this group of individuals” following recent steps by America to reduce the numbers held at the prison, the Foreign Office said in a statement in London. “They have decided to request the release and return of the five detainees who have links to the U.K. as former residents.” The detainees whose release they will request are Shaker Aamer, Jamil El Banna, Omar Deghayes, Binyam Mohamed, and Abdennour Sameur, the Foreign Office said.

A State Department spokesman, Sean McCormack, said the British government sent a letter to the Bush administration requesting the release of the five detainees. “We have the letter and we’re going to review the request consistent with our policies,” Mr. McCormack told reporters yesterday in Washington.

“As you know, our policy has been for quite some time to work with countries who have an interest in either having their nationals return or taking responsibility for third-country nationals,” he added.

As of July 16, about 80 detainees determined eligible for transfer or release remained at Guantanamo, according to the Defense Department. In all, about 360 people were being held at the prison.

All nine British citizens originally held at Guantanamo were set free upon their return to Britain. Five were released in March 2004. The remaining four were sent back in January 2005.

Mr. Brown took over on June 27 when Prime Minister Blair stepped aside after a decade in office. Mr. Brown appointed David Miliband as foreign secretary and Jacqui Smith as home secretary. The British request may be refused, according to Bob Ayers, an associate fellow at Chatham House, a London-based foreign policy analysis center. “It will be a combination of two things: how dangerous the U.S. thinks these people are, and what assurances the U.K. can give that they will prevent them reverting to terrorism,” Mr. Ayers, who spent 30 years in U.S. military intelligence, said.

Mr. El Banna was arrested in Gambia in November 2002, according to a July 25 report by Parliament’s Intelligence and Security Committee, which questioned British intelligence agencies about his case.

British agents had previously questioned Mr. El Banna, suspecting him of financing an Islamic cleric currently being held on suspicion of recruiting for Al Qaeda, Abu Qatada. Even after requests to American colleagues from British intelligence that he should not be held, he was transferred first to Afghanistan and then to Guantanamo.

If America agrees to return the men, they would be subject to “the same security considerations and actions as would apply to any other foreign national,” according to the Foreign Office statement.