WASHINGTON (AFP) - The Pentagon will on Monday announce that 15 inmates have been transferred from the Guantanamo Bay military prison in Cuba, in what would be the largest such release in recent years, Amnesty International USA said.
The Pentagon declined to comment, but if confirmed, the transfers would bring the number of detainees left at Guantanamo down to 61.
"It's a significant repudiation of the idea that Guantanamo is going to be open for business for the indefinite future," Naureen Shah, Amnesty International USA's security and human rights programme director, told AFP.
Amnesty emphasised that the group had not yet seen the Pentagon announcement.
But Shah said all of the men appeared to be destined for the United Arab Emirates.
One of those expected to be transferred is an Afghan called Obaidullah, who allegedly had hidden land mines in 2001. He was detained for 14 years without trial.
The Guantanamo prison has held about 780 inmates in all since it was opened shortly after the US-led invasion of Afghanistan in late 2001.
President Barack Obama urgently wants to close the facility before he leaves office at the start of next year but has been continually thwarted by Republican lawmakers.
The United States has in recent months accelerated the rate at which detainees who have been approved for transfer are released from the facility.
If Amnesty's numbers are confirmed, 19 inmates will remain who have been cleared for transfer.
Obama wants to send the rest, deemed to be the most dangerous, for incarceration in the United States - but that is an extreme longshot given Republican opposition.
To date, just 10 of the detainees face criminal trial, including the "9/11 Five" who are accused of plotting the September 11, 2001 attacks.
Shah said it was important for Obama to push ahead with plans to shutter Guantanamo, or the next administration could start to once more fill its cells with suspected Islamic militants captured in the campaign against the Islamic State in Iraq and Syria group.
Guantanamo is a US naval base carved out of a remote chunk of land on the tip of southeastern Cuba. The administration of George W Bush opened a prison there to hold terror suspects.