WASHINGTON — The United States has transferred two Libyan detainees from Guantanamo Bay to the African nation of Senegal, another small step in President Obama's strategy to close the detention facility.

The transfers, announced Monday, bring the total number of detainees at the naval base to 87. And it continues an effort to find homes in third countries for detainees from trouble spots like Libya, Syria and Yemen — where the United States won't return detainees either because of humanitarian or security concerns.

With the two Libyans, Senegal has become the 26th such country to accept Guantanamo detainees since 2009. Secretary of State John Kerry said the United States was "very grateful" to Senegal for "offering humanitarian resettlement."

With less than 10 months in Obama's presidency, the administration is finding increasingly difficult cases to put to the Periodic Review Board, the six-agency body that reviews each case to decide whether to try or release each detainee.

And the transfers have come under increasing criticism from Capitol Hill, in part because of concerns they'll return to the battlefield. A congressionally required report from the Office of the Director of National Intelligence last month estimated that 204 former Guantanamo detainees have engaged in jihadist activities. But 185 of those were released during the George W. Bush administration.

The two transferred Libyans are:

► Salem Abdu Salam Ghereby, 55, identified by the Pentagon as a "former explosives trainer and veteran jihad fighter." He was arrested by Pakistani security forces in 2001 after crossing the border from Afghanistan.

► Omar Khalif Mohammed Abu Baker Mahjour Umar, born in 1972, was the "commander of a militant training camp and acknowledged serving as trainer," according to a Pentagon report. He was captured in a 2002 raid of a suspected al-Qaeda safe house in Pakistan.

The Periodic Review Board unanimously determined that neither Libyan posed a security risk.