WASHINGTON -- The Pentagon says the Guantanamo Bay prison meets the standard for humane treatment laid out in the Geneva Conventions, according to a report for President Barack Obama, who has ordered the terrorist detention center closed within a year.

The report recommended some changes, including an increase in group recreation for some of the camp's more dangerous or less compliant prisoners, according to a government official familiar with the study. The report also suggested allowing those prisoners to gather in groups of three or more, said the official, who spoke on condition of anonymity because the report has not officially been released.

Some of the hard-core prisoners are not currently allowed to meet with other prisoners for prayer or socialization and are kept in their cells for 23 hours a day.

Alleged Sept. 11 mastermind Khalid Sheik Mohammed is among the prisoners who could be affected by the change. Prolonged social isolation has been known to harm mental health among prisoners.

The 85-page report by Adm. Patrick M. Walsh, the Navy's second in command, was written in response to Obama's Jan. 22 executive order to close the facility at Guantanamo Bay, Cuba within a year.

As a presidential candidate, Obama criticized the detention center that human rights groups and many in the international community widely condemned for harsh treatment of prisoners during the Bush administration. The military has defended its actions, saying prisoners have been treated humanely since the center was set up after the Sept. 11, 2001 terrorist attacks.

The report found the camp to be in compliance with the Geneva Conventions Common Article 3, the international rules that require the humane treatment of prisoners taken in unconventional armed conflicts, like the war on terrorism. The camp's controversial force-feeding of prisoners on hunger strikes was also found to be compliant with the Geneva guidelines, a second government official confirmed.

Last month, the military judge in charge of deciding whether to charge Guantanamo detainees with crimes told The Washington Post at least one of the prisoners was tortured in 2002 and 2003, alleged Sept. 11 conspirator Mohammed al-Qahtani.

About 800 prisoners have been held there, many for years and nearly all without criminal charges. There are now around 250, including 17 from China who the United States wants to set free but cannot return to China for fear they will be tortured by the government.

Guantanamo was selected for legal reasons: as a military base, it is sovereign U.S. territory but, according to Bush administration lawyers, was outside the scope of the Constitution. That would allow prisoners to be prosecuted for war crimes using evidence that would be difficult to use in the U.S. civilian court system.