President Obama revealed Thursday that four more detainees have been transferred out of the Guantanamo Bay detention facility as he took a parting shot at Congress for blocking his eight-year effort to close the prison.

In a letter to the Republican leaders of Congress, Obama said that 41 detainees remain, down from the 45 the Pentagon said were there Tuesday.

“Of the nearly 800 detainees at one time held at the facility, today only 41 remain,” Obama wrote a letter to Speaker Paul Ryan Paul Davis RyanAt indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates Peterson faces fight of his career in deep-red Minnesota district MORE (R-Wis.) and Senate President Pro Tempore Orrin Hatch Orrin Grant HatchBottom line Bottom line Senate GOP divided over whether they'd fill Supreme Court vacancy MORE (R-Utah).

ADVERTISEMENT

“There is simply no justification beyond politics for the Congress' insistence on keeping the facility open,” Obama continued later. “Members of Congress who obstruct efforts to close the facility, given the stakes involved for our security, have abdicated their responsibility to the American people.”

The letter and an accompanying report on the Obama administration’s efforts to close the facility do not name the newly transferred detainees or what countries they were sent to.

Saudi Arabia state news agency SPA reported that Saudi citizen Jubran bin Saad bin Waze' Al-Qahtani returned to the kingdom from Guantanamo on Thursday night.

Of those remaining at the facility, five have been cleared for transfer by the Obama administration, 10 have been charged or convicted by military commissions and the rest are considered too dangerous to release but can’t be tried by the commissions.

President-elect Donald Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE has said he wants to fill Guantanamo up with “bad dudes,” while his chosen Defense secretary, retired Gen. James Mattis, has talked about the need to hold detainees until the end of the conflict.

Obama promised in his first campaign for the presidency to close Guantanamo, but he was repeatedly blocked by Congress. In particular, Congress banned transfers to the United States, which Obama’s closure plan relied on.

ADVERTISEMENT

In his letter, Obama said the bans on transfers “make no sense.”

“No person has ever escaped one of our super-max or military prisons here, ever,” he said.

Obama added that “history will cast a harsh judgment” on the failure to close the facility and encouraged Congress one last time to close it.

The letter and the report reiterated many of the same arguments Obama has made for years, including that the facility serves as a propaganda tool for terrorists and that it is too costly.

According to the report, it cost $445 million to operate Guantanamo in fiscal 2015. There is also $200 million in needed military construction, and $25 million for related furnishing, according to the report. By contrast, the report says, moving detainees stateside would save about $85 million per year.

“As the president has said, spending hundreds of millions of dollars to keep 41 men in an isolated detention facility in Cuba, year after year, is not consistent with our values or our interests as a nation,” the report concludes. “It undermines our standing in the world, and it is viewed as a stain on our longstanding record of upholding the highest standards, of adhering to the rule of law. It is long past time to close this chapter in our history.”

Updated at 3:57 p.m.