White House spokesman Tony Snow said the policy, outlined in a new Defense Department memo, reflects the recent 5-3 Supreme Court decision blocking military tribunals set up by President Bush. That decision struck down the tribunals because they did not obey international law and had not been authorized by Congress.
The policy, described in a memo by Deputy Defense Secretary Gordon England, appears to reverse the administration's earlier insistence that the detainees are not prisoners of war and thus subject to the Geneva protections.
"This is a direct result of the Supreme Court's big terror law ruling last month when five Justices ruled that the Administration's plans to try the Guantanamo Bay detainees violated the Geneva Conventions," CBS News legal analyst Andrew Cohen said.
Word of the Bush administration's new stance came as the Senate Judiciary Committee opened hearings Tuesday on the politically charged issue of how detainees should be treated.
Click here to read the Department of Defense memo.
"We're not going to give the Department of Defense a blank check," Republican Sen. Arlen Specter of Pennsylvania, the committee chairman, told the hearing.
Sen. Patrick Leahy of Vermont, the committee's top Democrat, said "kangaroo court procedures" must be changed and any military commissions "should not be set up as a sham. They should be consistent with a high standard of American justice, worth protecting."
Snow insisted that all U.S. detainees have been treated humanely. Still, he said, "We want to get it right."
"It's not really a reversal of policy," Snow asserted, calling the Supreme Court decision "complex."
The principal deputy general counsel of the Department of Defense told Senators that detainees in Guantanamo are already being treated in accordance with Article 3 of the Geneva Conventions, which specifies how prisoners must be treated, CBS News correspondent Bob Fuss reports.
Steven Bradbury, acting assistant attorney general of the Justice Department's Office of Legal Counsel, told the Senate hearing that the Bush administration would abide by the Supreme Court's ruling that a provision of the Geneva Conventions applies.
But he acknowledged that the provision, which requires humane treatment of captured combatants and requires trials with judicial guarantees "recognized as indispensable by civilized people," is ambiguous and would be hard to interpret.
"The application of common Article 3 will create a degree of uncertainty for those who fight to defend us from terrorist attack," Bradbury said.
The Pentagon stands to gain a lot from this change of policy, Cohen says. "Now, arguably, our own soldiers around the world have a better chance to gain the protections of the Geneva Conventions from enemy states. I think the reciprocity issue here was a big factor," Cohen added.
Snow said efforts to spell out more clearly the rights of detainees does not change the president's determination to work with Congress to enable the administration to proceed with the military tribunals, or commissions. The goal is "to find a way to properly do this in a way consistent with national security," Snow said.
Snow said that the instruction manuals used by the Department of Defense already comply with the humane-treatment provisions of Article 3 of the Geneva Conventions. They are currently being updated to reflect legislation passed by Congress and sponsored by Sen. John McCain, R-Ariz., to more expressly rule out torture.
Speaking after the Supreme Court issued its ruling, President Bush said he would work with Congress to get approval to try terrorism suspects before military tribunals.
On June 29, Mr. Bush said the ruling "won't cause killers to be put out on the street," and added that he "will not jeopardize the safety of the American people."
"The administration intends to work with Congress," Snow said.
"We want to fulfill the mandates of justice, making sure we find a way properly to try people who have been plucked off the battlefields who are not combatants in the traditional sense," he said.
"The Supreme Court pretty much said it's over to you guys (the administration and Congress) to figure out how to do this. And that is where this is headed.