The US has just missed a deadline to close the prison camp
A task force on the US prison camp at Guantanamo Bay, Cuba, has advised that 47 inmates should be held indefinitely without trial, officials say.
It is thought to be the first time that officials have given a figure for those who might be held without charge.
A US civil liberties group has said detainees should not be held without due process in Guantanamo or elsewhere.
The news came as the deadline US President Barack Obama had set himself for closing the prison camp passed.
The task force, led by the US justice department, recommended that while 35 people could be prosecuted through trials or military tribunals, 110 could be released either now or at a later date, unnamed officials said.
The other nearly 50 detainees are considered too dangerous to release, but cannot be tried because the evidence against them is too flimsy or was extracted from them by coercion, so would not hold up in court.
Congress has laid down that only those to be tried can be moved to US soil, so the question of what to do with those to be detained indefinitely without trial has yet to be resolved.
The BBC's Adam Brookes says the outcome will dismay many of Mr Obama's supporters, who had hoped the president would end the practice of detention without trial.
The American Civil Liberties Union was quick to react to the task force's reported recommendations.
"Just as important as closing the prison quickly is closing it right, and that means putting an end to the illegal policy of indefinite detention without charge or trial," said the group's executive director, Anthony Romero.
"This practice was wrong in Cuba and would remain so here [in the US], reducing the closure of Guantanamo to a symbolic gesture."
A White House official stressed that this was only a recommendation, which Mr Obama does not have to accept.
The task force's findings are subject to review by the National Security Council.
More than 40 detainees have been transferred out of the prison under the Obama administration.
But diplomatic hurdles and domestic opposition to the government's plan to house suspects on US soil have hampered his plans to close it down completely.
Plans to move detainees approved for trial to a prison facility in Illinois remain under consideration.
The task force recommended that among those cleared for release, 80 detainees, including about 30 Yemenis, could be freed immediately, the Washington Post said.
The panel said the release of another 30 Yemenis should be contingent on an improved situation in Yemen, the newspaper reported.
However, the US recently suspended the repatriation of Yemeni prisoners indefinitely, following an airliner bomb plot that was allegedly planned in Yemen.
Yemenis account for approximately half of the inmates at Guantanamo.
Mr Obama set himself the 22 January deadline a year ago, shortly after being sworn in.
He has subsequently said he wants the camp closed this year, without setting a specific deadline.