By Matt Spetalnick and Idrees Ali
WASHINGTON (Reuters) - The United States sent four more detainees from the Guantanamo Bay military prison to two other countries on Thursday, marking President Barack Obama's final prisoner transfers from a facility whose continued existence he said would be judged harshly by history.
With Republican Donald Trump to be sworn in as president on Friday and vowing to keep the prison open, Democrat Obama whittled down the inmate population there to only 41, far short of fulfilling his promise to close the jail dating back to his 2008 presidential campaign.
In a parting shot on an issue seen tarnishing his legacy, Obama said U.S. lawmakers who have thwarted his efforts to shut the prison at the U.S. naval base in Cuba "have abdicated their responsibility to the American people."
"History will cast a harsh judgment on this aspect of our fight against terrorism and those of us who fail to bring it to a responsible end," he said in a letter to the Republican-controlled Congress. "Once again, I encourage the Congress to close the facility."
It was opened by Obama's predecessor President George W. Bush to hold terrorism suspects who had been rounded up overseas after the Sept. 11, 2001 attacks. Under Bush's administration it came to symbolize harsh detention practices that opened the United States to accusations of torture.
The latest transfers completed a final flurry in the waning days of Obama's eight-year tenure.
A U.S. official, speaking on condition of anonymity, said four prisoners had departed but did not identify the two countries. The White House declined comment.
Other officials had earlier told Reuters the United Arab Emirates would be among the places taking Guantanamo inmates. Saudi Arabia and Oman have taken 14 detainees in recent weeks.
Trump said during the election campaign that he not only wants to keep the Guantanamo prison open but "load it up with some bad dudes."
The Obama administration pressed ahead, however, moving out most of the prisoners on a list of low-level detainees deemed by parole-style inter-agency reviews to be safe for transfer. There were 242 prisoners when he took office.
His efforts were blocked by mostly Republican opposition in Congress, which barred him from moving prisoners to the U.S. mainland. Foot-dragging by Pentagon officials has also been blamed for slowing transfers.
Obama lamented on Thursday that his opponents had "placed politics above the ongoing costs to taxpayers, our relationships with our allies, and the threat posed to U.S. national security."
Trump said this month that all those held at Guantanamo should stay. "These are extremely dangerous people and should not be allowed back onto the battlefield," he tweeted.
However, the Obama administration has insisted that intelligence shows that only a very small percentage of the prisoners it has released have returned to militant activities.
Of the 41 prisoners left at Guantanamo, 10 face charges in military commission proceedings, including people accused of plotting the Sept. 11 attacks. About two dozen others have not been charged but have been deemed too dangerous to release.
In addition, a handful of inmates previously cleared for transfer will remain after the Obama administration failed to make arrangements in time for their relocation.
(Reporting By Matt Spetalnick and Idrees Ali; Editing by Andrew Hay and Grant McCool)