"All of the prisoners held at Guantanamo should be charged or released," said Vienna Colucci, international justice specialist with Amnesty International USA.
Colucci was responding to news the Defense Department will transfer prisoners out of its high-security Guantanamo Bay jail, where some have been held a year and a half and all are held without charges or lawyers.
It was unclear whether the prisoners would go free or merely be returned to their countries for continued detention or charges.
"Those no longer detained by the United States should under no circumstances be forcibly returned to countries where they would be at risk of unfair trial, torture or other cruel, inhuman or degrading treatment," Colucci said in a statement.
Some 660 prisoners from 42 countries are held, many captured during the war in Afghanistan against the al Qaeda terror network. Officials refuse to identify them or their countries or say exactly how many are held.
An official said Monday that he believed juveniles were among those to be released this week. News that several boys aged 13 to 16 are held at Guantanamo has drawn criticism from human rights groups and demands for their immediate release.
One official said 20 to 30 prisoners would be released from the prison, which was opened in January 2002. Another said the number was 12 to 15.
Defense officials speaking on condition of anonymity denied that the release stems from a complaint by U.S. Secretary of State Colin Powell, who pressed the Pentagon to move faster in determining the fate of the prisoners.
In what officials have said was a strongly worded letter, Powell told U.S. Defense Secretary Donald H. Rumsfeld on April 14 that eight allies had complained about the holding of their citizens. He said the situation undermines efforts to win international cooperation in the war on terror.
The release has been in the planning process for several weeks, Pentagon officials said. One official said juveniles had been among those planned for release weeks ago, but it was delayed because the military was busy with the war to disarm and depose Saddam Hussein in Iraq.
Human Rights Watch said the United States was exacerbating a contentious situation.
The detention of youths "reflects our broader concerns that the U.S. never properly determined the legal status of those held in the conflict," said James Ross, legal adviser for Human Rights Watch in New York.
Holding "captured children … obviously makes the problem worse."
Officials said long ago that some prisoners could be released to their countries if it were certain their governments would deal with them properly. Talks have been under way with various countries, but no results have been announced.
Countries that have said publicly they want their citizens home include Russia, Saudi Arabia, Sweden, Britain and Pakistan. Officials said they didn't know the home countries of the prisoners to be released.
Colucci said it's unfair to give special treatment to prisoners from allied countries.
"The United States should guarantee prompt and fair review of all prisoners' cases and not restrict this action to nationals of particular allied countries," Colucci said.
Since the prison was opened, only 23 people are known to have been released.
Rumsfeld said Sunday that the process for releasing prisoners is complicated and slow. They must be questioned by several government agencies, including the FBI, the Justice Department, the State Department, the Pentagon, the CIA and U.S. immigration services, he said.
"That's not an excuse we'd accept when talking about processing a driver's license application. And we're talking about depriving people of their liberty," said Amnesty spokesman Alistair Hodgett. "It's hard to see why it should take 500 days to determine whether an individual should be charged with a crime or set free."
The defense secretary said he, too, would like to see the process move faster.
Rumsfeld has said over the past year that the first priority was to interrogate the prisoners for information on future terrorist activities or terror networks. He said they could be released if it were determined there would be no charges against them, they posed no threat and they had no more useful intelligence to offer.
Pentagon officials said Friday that they had finished writing rules for trying terrorist suspects in military tribunals.
Two months after the Sept. 11, 2001, terror attacks in Washington and New York, President Bush authorized establishment of tribunals to try foreign suspects in the counterterror war.
Speaking on condition of anonymity, the officials said they have some suspects in mind who might be candidates. They offered no number of planned trials, nor dates they might start and said no final decisions have been made.