The top US general in Iraq authorised interrogation techniques including the use of dogs, stress positions and disorientation, a memo has shown.
The ACLU said the measures had gone beyond the acceptable
The document was obtained by the American Civil Liberties Union through the US Freedom of Information Act.
The September 2003 document is signed by the then commander of US forces in Iraq, Gen Ricardo Sanchez.
The ACLU says the measures go beyond generally accepted practice and says Gen Sanchez should be made accountable.
The memo authorised techniques including putting prisoners in stressful positions, using loud music and light control, and changing sleeping patterns.
It also authorised the presence of muzzled military working dogs to, as the memo puts it, "exploit Arab fear of dogs while maintaining security during interrogations".
The presence of dogs and other measures, all of which required approval by Gen Sanchez, were rescinded a month later because of opposition from military lawyers.
Gen Sanchez says advance permission was required every time one of these techniques was requested, adding that he never gave such permission.
'Beyond army limits'
The Pentagon originally refused to release the memo on national security grounds, but passed it to the ACLU on Friday after the union challenged it in court under the Freedom of Information Act.
The ACLU says at least 12 of the 29 techniques listed in the document went far beyond limits established by the army's field manual.
"Gen Sanchez authorised interrogation techniques that were in clear violation of the Geneva Conventions and the army's own standards," ACLU lawyer Amrit Singh said in the union's statement.
Gen Sanchez was commander from June 2003 to July 2004
"He and other high ranking officials who bear responsibility for the widespread abuse of detainees must be held accountable."
The techniques included "environmental manipulation" such as making a room hot or cold or using an "unpleasant smell", isolating a prisoner, and disrupting normal sleep patterns.
The memo also allowed the "false flag" technique of "convincing the detainee that individuals from a country other than the United States are interrogating him."
It was during Gen Sanchez's time as commander that Iraqi prisoners were abused by US troops at Baghdad's Abu Ghraib prison.
The cases - highlighted in photographs of hooded and naked inmates - sparked international outrage.
Army investigations have generally found that, where proven, abuses were not the result of policy set by senior leaders.
The ACLU is currently taking part in a lawsuit against Defence Secretary Donald Rumsfeld accusing him of responsibility for torture and abuse of detainees in US military custody in Iraq and Afghanistan.