The Pentagon announced Monday the transfer of two Libyan inmates from the Guantanamo Bay detention centre to Senegal, the latest move under President Barack Obama's contentious plan to shutter the notorious jail.

The two men -- Salem Abdu Salam Ghereby, 55, and Omar Khalif Mohammed Abu Baker Mahjour Umar, approximately 44 -- had been in the US military prison located in Cuba since 2002.

Both had ties to the Libyan Islamic Fighting Group and Al-Qaeda, according to their leaked prisoner files.

"The United States is grateful to the government of Senegal for its humanitarian gesture and willingness to support ongoing US efforts to close the Guantanamo Bay detention facility," the Pentagon said in a statement.

For its part Senegal said Monday it was glad to support the "historic" US decision to close Guantanamo.

"It is in the tradition of Senegalese hospitality and Islamic solidarity towards two African brothers who have expressed their wish to be resettled in Senegal after their release," read a foreign ministry statement, released by the national APS news agency.

The latest transfers mean the remaining population at the controversial jail inow stands at 89. Thirty-five of them have been approved for release to other countries, though the complex process is only completed after rehabilitation and monitoring measures are implemented.

Obama had promised, on his second day in office in 2009, to close the Guantanamo prison within a year, but his efforts floundered largely due to fierce opposition from Republican lawmakers.

In February, the president presented Congress with a new closure plan for Guantanamo, which he says serves only to stoke anti-US resentment and fuel jihadist recruitment.

But the plan is likely doomed.  Republicans continue to oppose the jail's shuttering, especially because Obama wants to transfer the highest-risk detainees to a site in the United States. 

"The administration is determined to close the Guantanamo Bay detention facility. The continued operation of the detention facility weakens our national security by draining resources, damaging our relationships with key allies and partners and serving as a propaganda tool for violent extremists," Secretary of State John Kerry said in a statement.

Senegal is one of 26 countries that have agreed to resettle nearly 100 detainees since 2009.

"This significant humanitarian gesture is consistent with Senegal's leadership on the global stage," Kerry said.

'Erase the stain of Guantanamo'

Human Rights Watch said the latest transfers signalled "meaningful progress," but warned that the Pentagon needs to accelerate its pace of transferring detainees if Obama is to close Guantanamo before he leaves office in January 2017.

"Senegal's decision to welcome the two Libyans will help heal the harm the 14 years of unjust detention at Guantanamo has caused them," said Laura Pitter, senior US national security counsel at the rights campaign group, in a statement.

"Obama has less than a year in office to erase the stain of Guantanamo that taints his human rights legacy," Pitter added.

Mahjour Umar had been held on suspicion of helping re-establish Al-Qaeda camps in Afghanistan following their destruction by US bombings in 1998, and was identified as an explosives and weapons trainer, according to his leaked file.

Ghereby's file says he had attended multiple training camps and received explosives training from a senior Al-Qaeda explosives expert. Neither man was ever charged.

The Pentagon said the men were approved for transfer after multiple agencies reviewed their cases.

Guantanamo Bay is a US naval base carved out of a remote chunk of land on the tip of southeastern Cuba. The administration of president George W. Bush opened a prison there to hold terror suspects soon after the US-led invasion of Afghanistan in late 2001.

In all, it has housed about 780 inmates over the years. 

Republican presidential candidates have vowed that, if elected, they would send more terror suspects to Guantanamo instead of closing it.