The US government last year approved interrogation techniques for use at its detention facility in Guantanamo Bay, Cuba, that permit reversing the normal sleep patterns of detainees and exposing them to heat, cold, loud music and bright lights, The Washington Post reported on its website on Saturday.
Citing unnamed defence officials, the newspaper said a classified list of about 20 techniques was approved at the highest levels of the Pentagon and the Justice Department in April 2003.
The list represents the first official policy permitting interrogators to use physically and psychologically stressful methods, the paper added.
The use of any of these techniques requires the approval of senior Pentagon officials and, in some cases, of the defence secretary, according to the report.
Interrogators must justify that the harshest treatment is "militarily necessary," The Post cited one of the officials as saying. Once approved, the harsher treatment must be accompanied by "appropriate medical monitoring," the paper said.
"We wanted to find a legal way to jack up the pressure," The Post quoted one of the lawyers involved in writing the guidelines as saying. "We wanted a little more freedom than in a US prison, but not torture."
Under the guidelines, some prisoners could be made to stand for four hours at a time, the report said.
Questioning a prisoner without clothes is permitted if he is alone in his cell, but any physical contact is banned.
Defence and intelligence officials said similar guidelines had been approved for use on "high-value detainees" in Iraq - those suspected of terrorism or of having knowledge of insurgency operations, according to the report.
The Central Intelligence Agency has its own guidelines used in detention centres. It could not be learned whether similar guidelines were in effect at the Abu Ghraib prison outside Baghdad, the paper said.
But lawmakers have said they want to know whether the misconduct reported there was an aberration or whether it reflected an aggressive policy taken to inhumane extremes.
Pictures taken at Abu Ghraib show Iraqi prisoners forced by prison personnel into sexually explicit and degrading poses, ordered to wear women's underwear over their heads, or held on a dog leash by a US female prison guard.
The Pentagon guidelines for Guantanamo were designed to give interrogators the authority to prompt uncooperative detainees to provide information, though experts on interrogation say information submitted under such conditions is often unreliable, The Post said.