The US government today defended the use of the interrogation technique known as waterboarding, saying it is legal - not torture, as critics argue - and has saved American lives.
President George Bush would authorise waterboarding for future terrorism suspects if certain criteria are met, a spokesman said.
Waterboarding involves strapping a suspect down and pouring water over his cloth-covered face to create the sensation of drowning. It has been traced back hundreds of years, to the Spanish Inquisition, and is condemned by nations around the world.
Yesterday, the Bush administration acknowledged publicly for the first time that the tactic was used by US government interrogators on three terror suspects.
Testifying before Congress, CIA director Michael Hayden said Khalid Sheikh Mohammed, Abu Zubaydah and Abd al-Rahim al-Nashiri were waterboarded in 2002 and 2003.
Mr Hayden banned the technique for CIA interrogations in 2006, the US Defense Department has banned its employees from using it, and FBI director Robert Mueller said his investigators do not use coercive tactics in interviewing terror suspects.
Senate Democrats demanded a criminal investigation after Mr Hayden's revelation.
Mr Bush personally authorised Mr Hayden's testimony, White House deputy spokesman Tony Fratto said.
Mr Fratto said: "There's been a lot written out there - newspaper, magazine articles, some of it misinformation.
"And so the consensus was that on this one particular technique that these officials would have the opportunity to address them - in not just a public setting, but in a setting in front of members of Congress, and to be very clear about how those techniques were used and what the benefits were of them."
Mr Fratto said CIA interrogators could use waterboarding again, but would need the president's approval to do so. That approval would "depend on the circumstances", with one important factor being "belief that an attack might be imminent", Mr Fratto said.
"The president will listen to the considered judgment of the professionals in the intelligence community and the judgment of the attorney general in terms of the legal consequences of employing a particular technique," he said.
"The president will listen to his advisers and make a determination."
Mr Fratto said waterboarding's use in the past was also approved by the attorney general, meaning it was legal and not torture.
Officials fear that calling waterboarding torture or illegal could expose US government employees to criminal or civil charges or even international war crimes charges.
"Every enhanced technique that has been used by the Central Intelligence Agency for this programme was brought to the Department of Justice and they made a determination that its use under specific circumstances and with safeguards was lawful," Mr Fratto said.
Critics say waterboarding has been outlawed under the UN's Convention Against Torture, which prohibits treatment resulting in long-term physical or mental damage.
They also say it should be recognised as banned under the US 2006 Military Commissions Act, which prohibits treatment of terror suspects that is described as "cruel, inhuman and degrading". The act does not explicitly prohibit waterboarding by name.
Human Rights Watch, which has been calling on the US government to outlaw waterboarding as a form of illegal torture, called Mr Hayden's testimony "an explicit admission of criminal activity".