President Barack Obama presented a long-shot plan Tuesday to shutter the Guantanamo Bay detention centre, hoping to fulfill an elusive campaign promise before he leaves office next year.
Describing the jail as a stain on America's reputation and a catalyst for jihadists, Obama said "I don't want to pass this problem on to the next president."
"For many years, it's been clear that the detention facility at Guantanamo Bay does not advance our national security. It undermines it," Obama said from the White House's Roosevelt Room.
He outlined a $290-475 million plan to move the 91 remaining detainees abroad and to one of 13 possible — unnamed — facilities in the United States.
Obama has tried for almost eight years to close the jail, but has been thwarted by Congress, the Pentagon, some in his own party and foreign allies who refuse to host the terror suspects abroad.
As a candidate and as president, Obama has argued that the indefinite detention without trial of Guantanamo inmates harms America's image and its national security.
"It undermines our standing in the world," he said. "This is about closing a chapter in our history."
Lawmakers in the Republican-controlled Congress have blocked the most obvious path to closing the facility by banning the transfer of detainees to the United States, and there is little prospect of Republicans changing tack in the runup to the November presidential election.
House Speaker Paul Ryan immediately rejected the proposal, saying bringing "Guantanamo terrorists" to the United States was neither smart nor safe.
"It is against the law, and it will stay against the law, to transfer terrorist detainees to American soil," he added.
Obama appealed for the closure plan to be given "a fair hearing, even in an election year."
But Senator Marco Rubio, a Republican presidential candidate, doubled down on opposing it, promising to increase the Guantanamo population if elected.
"Not only are we not going to close Guantanamo — when I am president, if we capture a terrorist alive... they are going to Guantanamo and we are going to find out everything they know," he said.
Obama also has faced opposition from within his own administration, with the Pentagon accused of slow-pedalling transfers and overstating closure costs.
The president could still try to force the closure through an executive order, but such a move would expose him to accusations of ruling by decree.
Obama got strong backing from one prominent Democrat, presidential contender Hillary Clinton.
"Closing Guantanamo would be a sign of strength and resolve," she said, urging Congress to implement the plan "as quickly and responsibly as possible."
Her campaign also pointed to her efforts to help close the facility while serving as Obama's secretary of state.
The Guantanamo Bay closure plan, which took months to produce, offers no specifics on the potential location of a US facility.
But military officials have previously listed Fort Leavenworth, Kansas, or the US Navy brig in Charleston, South Carolina, among possible destinations for inmates.
Those locations, however, face objections from local politicians.
Obama has long argued that many Guantanamo prisoners should be transferred overseas and some should be tried by military courts.
A small number — those deemed too dangerous to release but too difficult to prosecute — would be held in the United States.
Human rights groups worry this would only extend detentions without trial and create a "Guantanamo North."
"The possibility of a new, parallel system of lifelong incarceration inside the United States without charge would set a dangerous precedent," Amnesty International said in a statement.
The plan says a US facility would save money over time. It currently costs about $455 million each year to run Guantanamo, and a US site would reduce that amount by up to $180 million.
Most of the savings would come from a decrease in the number of troops guarding the reduced population on the US mainland, although it could cost up to $475 million in one-time expenses to move the men and build or update a facility to hold them.
Efforts to transfer prisoners overseas have been stymied by unrest in Yemen — a likely destination for many — and by recidivism among those already released.
Still, Defense Secretary Ashton Carter has in recent weeks signed off on a flurry of transfers, and last month, the prison's population dropped below 100 for the first time.
Today, 91 inmates remain. Of them, 35 have been approved for release. The rest face ongoing, indefinite detention.
Perhaps the most notorious prisoner is Khalid Sheikh Mohammed, who along with four co-defendants is charged with plotting the September 11, 2001, attacks.
Guantanamo opened in January 2002 on a US naval base on a coastal spit of land in southeastern Cuba leased from Havana under a treaty dating back to 1903.
It was set up after the 9/11 attacks under then-president George W. Bush's administration to deal with "enemy combatants" denied many US legal rights.