Outgoing Defense Secretary Donald Rumsfeld authorized the mistreatment of detainees at Abu Ghraib prison in Iraq, the prison's former U.S. commander said in an interview on Saturday.

Former U.S. Army Brigadier General Janis Karpinski told Spain's El Pais newspaper she had seen a letter apparently signed by Rumsfeld which allowed civilian contractors to use techniques such as sleep deprivation during interrogation.

Karpinski, who ran the prison until early 2004, said she saw a memorandum signed by Rumsfeld detailing the use of harsh interrogation methods.

"The handwritten signature was above his printed name and in the same handwriting in the margin was written: "Make sure this is accomplished"," she told Saturday's El Pais.

The methods consisted of making prisoners stand for long periods, sleep deprivation ... playing music at full volume, having to sit in uncomfortably ... Rumsfeld authorized these specific techniques."

The Geneva Convention says prisoners of war should suffer "no physical or mental torture, nor any other form of coercion" to secure information.

"Prisoners of war who refuse to answer may not be threatened, insulted, or exposed to any unpleasant or disadvantageous treatment of any kind," the document states.