The country's spy chiefs were also warned that harsh techniques were likely to produce "unreliable information". But under pressure from the White House, the CIA brushed the concerns aside and approved a controversial interrogation programme for suspected al-Qaeda prisoners that included simulated drowning by waterboarding.

The military document described forms of extreme questioning as torture 13 times in two pages, just a month before government lawyers said the techniques did not reach that threshold and interrogators first used waterboarding against a captive.

The overview on "the use of physical/psychological coercion in interrogation" was sent in July 2002 by the Joint Personnel Recovery Agency (JPRA), which runs the programme to train US military personnel to resist torture if captured.