WASHINGTON - Military interrogators posing as FBI agents at the U.S. detention center at Guantanamo Bay, Cuba, wrapped terrorism suspects in an Israeli flag and forced them to watch homosexual pornography under strobe lights during interrogation sessions that lasted as long as 18 hours, according to one of a batch of FBI memos released Thursday.FBI agents working at the prison complained about the military interrogators' techniques in e-mails to their superiors from 2002 to 2004, 54 e-mails released by the American Civil Liberties Union showed. The agents tried to get the military interrogators to follow a less coercive approach and warned that the harsh methods could hinder future criminal prosecutions of terrorists because information gained illegally is inadmissible in court.

Maj. Gen. Geoffrey Miller, who was in charge of the prison at the time, overrode the FBI agents' protests, according to the documents.

Miller later left Guantanamo and was sent to Iraq under orders to find better ways of extracting intelligence from prisoners at Abu Ghraib and other American detention facilities. He advocated that guards help set the conditions for interrogations. Photos taken in Abu Ghraib in 2003 showed guards physically abusing and sexually humiliating prisoners.

The memos offer some of the clearest proof yet that the abuses and torture of prisoners in U.S. military custody weren't the isolated actions of low-ranking soldiers but a result of policies approved by senior officials, the ACLU said.

"These documents show that the abuse at Guantanamo and Abu Ghraib was not caused by rogue elements but rather it was the consequence of policies that were deliberately adopted by senior military and Pentagon officials," said Jameel Jaffer, an ACLU lawyer. "We think this should provide further reason to hold senior officials, not just low-ranking soldiers, accountable for the torture of prisoners."