US President Barack Obama has pledged a new push to close the prison at Guantanamo Bay, Cuba, amid a growing prisoner hunger strike there.
At the White House, Mr Obama said the detention centre was "contrary to who we are" and harmful to US interests.
He cited recent convictions of terror suspects to argue the civilian justice system was adequate for such trials.
Congress has blocked efforts to close the prison, but Mr Obama said he would renew discussions with lawmakers.
Mr Obama told reporters he had asked a team of officials to review operations at Guantanamo Bay and said he was not surprised there were problems there.
"It is inefficient, it hurts us in terms of our international standing, it lessens co-operation with our allies on counter-terrorism efforts, it is a recruitment tool for extremists, it needs to be closed," Mr Obama said.
'No longer necessary'
He described the detention facility at Guantanamo Bay as a "lingering problem" that would worsen if it remained open.
"I think it is critical for us to understand that Guantanamo is not necessary to keep America safe," Mr Obama told reporters.
Mr Obama added that with the war in Iraq ended and detention authority in Afghanistan transferred to Afghan forces, the facility in Cuba should also close.
He also said he would need the help of Congress to devise a long-term legal solution to the prosecution of detainees.
The president's comments come amid a hunger strike that has spread in recent weeks to include more than 100 of the 166 inmates at the facility.
They are protesting against their indefinite detention. Most are being held without charge.
In his remarks, the president seemed to support the US practice of force-feeding some hunger-strikers.
"I don't want these individuals to die," he said. "Obviously the Pentagon is trying to manage the situation as best we can."
The US has had to reinforce medical staff at Guantanamo Bay, with about 40 nurses and other specialists arriving at the weekend, according to a camp spokesman.
Soon after his election, Mr Obama made closing Guantanamo Bay a top priority for his new administration, pledging to close it within a year of his inauguration in January 2009.
But his plan to transfer prisoners to maximum security prisons in the US and try some detainees in the civilian justice system met fierce resistance from lawmakers of both parties.
Source: BBC News, April 30, 2013