Khalid Sheikh Mohammed, the alleged mastermind of the 11 September attacks in 2001, lied during interrogations after he was tortured by CIA agents, according to newly released documents.
Mohammed told US military officials he lied about the location of Osama bin Laden, the al-Qaeda network leader, because he had been tortured, according to transcripts of a 2007 hearing at Guantanamo Bay in Cuba where he is currently being held.
"I make up stories. Where is he? I don't know. Then he torture me," he said according to the transcripts released late on Monday.
"Then I said: 'Yes, he is in this area, or this is al-Qaeda' which I don't know ... I said no, they torture me."
However Mohammed, a Kuwaiti national who was captured in Pakistan in 2003, also freely claimed responsbility for almost 30 "terror" plots, the transcripts say.
The transcripts were released as part of a lawsuit in which the American Civil Liberties Union (ACLU) is seeking documents and details of the government's "terror" detainee programmes.
Most of the new material centres on detainees' claims of abuse in interrogations while being held overseas in CIA custody.
Previous accounts of the military tribunal hearings had been made public, but the administration of Barack Obama, the US president, reviewed the still-secret sections and determined that more could be released, although many portions were heavily altered.
The information increases pressure on the Obama administration to reveal more details about the mistreatment of such "terror" suspects and sparks fresh questions about intelligence tactics during the administration of George Bush, Obama's predecessor.
'Suffering and torture'
In the same transcripts another detainee, Abu Zubaydah, told the tribunal that he was tortured "for months" before US authorities concluded he was not the third main leader of the al-Qaeda network, as they had previously believed.
"[After months] of suffering and torture, physically and mentally, they did not care about my injuries,'' he is quoted as saying in the transcripts.
"After a few months went by, during which I almost lost my mind and my life, they made sure I didn't die."
Abu Zubaydah was the first detainee subjected to torture techniques, including the controversial practice of "waterboarding", designed to simulate the sensation of drowning, following approval by the Bush administration.
ACLU lawyer Ben Wizner called on the Obama administration on Tuesday to disclose more details, saying the new materials "provide further evidence of brutal torture and abuse in the CIA's interrogation programme".
He also said they demonstrated "beyond doubt that this information has been suppressed solely to avoid embarrassment and growing demands for accountability".
However George Little, a spokesman for the CIA spokesman, rejected the ACLU's allegations.
"The CIA plainly has a very different take on its past interrogation practices, what they were and what they weren't, and on the need to protect properly classified national security information," he said.