A Saudi detainee with residency status in Britain is expected to be freed from the US prison at Guantanamo Bay, Cuba in June following a campaign for his release.
Britain has made repeat calls since 2010 for the release of Shaker Aamer, who has a British wife and four children in London.
The 48-year-old is alleged to have been a key Britain-based recruiter and financier for Al-Qaeda and to have worked for Osama Bin Laden in Afghanistan.
Aamer, who has been held at Guantanamo without charge for more than 13 years, will likely be transferred to an undisclosed country over the summer, probably in June, along with up to 10 other detainees, a US government official told AFP on the condition of anonymity.
Those detainees include 46-year-old Moroccan Yunis Shokuri and 45-year-old Mauritanian Ahmed Abdel Aziz, who would be sent to their home countries, the source said, confirming a report in the Washington Post.
The official told AFP that the transfer will take place after a 30-day notice period to Congress, following a sign-off from Secretary of Defense Ashton Carter.
A total of 122 detainees remain at Guantanamo, 57 of whom have been deemed "releasable" by a review committee, including those slated for release this summer.
"The goal is to transfer all 57," said Lieutenant Colonel Myles Caggins, a Pentagon spokesman.
"We're going to support the president's mission of closing Guantanamo through transfers of detainees and prosecutions through military commissions," he said.
US President Barack Obama has repeatedly vowed to close the prison at the US naval base in Guantanamo Bay, Cuba.
Finding a host country for inmates who can't go home has been a major headache for the administration, however, with 48 Yemeni prisoners now unable to be repatriated due to conflict in their home country.