By Paul Reynolds
World affairs correspondent, BBC News website
The ICRC report implies the US violated international law
CIA interrogation techniques used on al-Qaeda suspects "constituted torture", according to a leaked report by the international Red Cross.
The findings were based on testimonies by 14 so-called "high-value" detainees who were held in secret CIA prisons.
They were interviewed after being transferred to Guantanamo Bay in 2006.
President George W Bush denied torture had happened and President Barack Obama has banned US agents from carrying out such practices.
The International Committee of the Red Cross (ICRC) has an international role in monitoring standards for prisoners and trying to ensure compliance by governments with the Geneva Conventions.
It was denied access to the prisoners until their transfer to Guantanamo Bay.
Among those interviewed by the ICRC was the alleged mastermind of the 9/11 attacks, Khalid Sheikh Mohammed, who said he was told he would be "brought to the verge of death and back".
The ICRC report was obtained by Mark Danner, a US writer, whose account is in the New York Review of Books.
The report was not intended for publication but, as is the procedure in such cases, was given in confidence to the US government.
"For the first time the words are those of the detainees themselves," Mark Danner says in a podcast attached to his story.
The report's table of contents lists the methods the prisoners told the ICRC they had endured.
Taken overall they constitute an attempt to break a prisoner down through sensory deprivation and beatings, none of which is supposed to leave physical damage that can be traced.
The accounts indicate that a combination of methods was used on each prisoner.
The methods listed included: Suffocation by water or waterboarding; prolonged stress standing; beating by use of a collar; confinement in a box; prolonged nudity; sleep deprivation and subjection to noise and cold water; and denial of solid food.
"They never used the word 'torture'... only to 'hard time'," Khalid Sheikh Mohammed is quoted as saying.
"I was never threatened with death, in fact I was told that they would not allow me to die, but that I would be brought to the 'verge of death and back again'."
He said he underwent waterboarding five times: "A cloth would be placed over my face, cold water from a bottle kept in a fridge was then poured onto the cloth by one of the guards so I could not breathe."
He said a clip was put on his finger to monitor his pulse "so they could take me to the breaking point".
'Minimise physical damage'
Another prisoner Abu Zubaydah was apparently the first to be subjected to this "alternative set of procedures".
He said: "I was told... that I was one of the first to receive those interrogation techniques, so no rules applied."
In his case, there was a variation apparently not used subsequently.
He said he was put into a tall box and later into a smaller one in which he had to crouch, causing a wound on his leg to start bleeding.
Prolonged stress standing
Confinement in a box
Denial of solid food
Source: ICRC Report
He also had a towel tied round his neck with which his interrogators would slam him against a wall, which had plywood attached to it.
Mr Danner surmised this was to minimise the physical damage caused to him.
With other prisoners this towel became a plastic collar used with the same effect.
President Bush acknowledged that, as he put it, an "alternative set of procedures" had been used on some prisoners but he denied this meant they had been tortured, which is outlawed by an international convention.
"The United States does not torture," President Bush said in September 2006. That was after the techniques described had been used.
The Bush administration developed a legal protection, under which the definition of torture was narrowed to exclude the methods described.
Barack Obama has outlawed practices like waterboarding
Mr Danner says the ICRC report now presents a "clear contradiction" of that position and that "this contradiction needs to be worked out".
Senator Patrick Leahy, chairman of the US's Senate Judiciary Committee, has proposed that former officials be given immunity in return for evidence.
Human rights groups want accountability.
President Obama has spoken of "looking forwards". He has also banned the use of the techniques by all US agencies, including the Central Intelligence Agency (CIA), which had been given special dispensation by the Bush administration.
The ICRC has said that it regrets the publication of the information attributed to its report.
There has been a counter attack by former Vice President Dick Cheney, who once said that the use of waterboarding had been, for him, a "no-brainer".
He accused President Obama of "making choices that, in my mind, will, in fact, raise the risk to the American people of another attack".
Some have questioned the value of the intelligence gained from harsh techniques.
Mr Cheney said: "I think those programmes were absolutely essential to the success we enjoyed of being able to collect the intelligence that let us defeat all further attempts to launch attacks against the United States after 9/11."