A long-running effort by the Bush administration to send home many of the terror suspects held at Guantánamo Bay, Cuba, has been stymied in part because of concern among United States officials that the prisoners may not be treated humanely by their own governments, officials said.

Earlier administrations have fired and prosecuted government officials who provided classified information to the press. They have also tried to force reporters to identify their sources.

But the Bush administration is exploring a more radical measure to protect information it says is vital to national security: the criminal prosecution of reporters under the espionage laws.