A retired CIA agent has said a top al-Qaeda suspect was interrogated using a simulated drowning technique, but that he believes it was justified.
John Kiriakou said he felt water-boarding may be torture
John Kiriakou told US broadcaster ABC that "water-boarding" was used when his CIA team questioned suspected al-Qaeda chief recruiter Abu Zubaydah.
He said it might be torture but that it "broke" the detainee in seconds.
US authorities are investigating the CIA's destruction of videotapes of al-Qaeda suspects being interrogated.
Mr Kiriakou said the day after water-boarding was used on Abu Zubaydah, the detainee told his interrogator that Allah had visited him in his cell during the night and told him to co-operate.
"From that day on, he answered every question," the retired agent said.
"The threat information he provided disrupted a number of attacks, maybe dozens of attacks."
But he added: "Like a lot of Americans, I'm involved in this internal, intellectual battle with myself weighing the idea that water-boarding may be torture versus the quality of information that we often get after using the water-boarding technique. And I struggle with it."
He said he felt water-boarding's use had "compromised [American] principles in the short term" and was unsure the technique would be justified any longer.
"At the time, I felt water-boarding was something we needed to do," he said.
"And as time has passed, and as September 11th has, you know, has moved farther and farther back into history, I think I've changed my mind."
The interview is said by ABC News to be first public comment by any CIA officer involved in handling top al-Qaeda suspects.
It comes as an official inquiry is launched into the CIA's destruction in 2005 of two videotapes showing interrogations of al-Qaeda suspects.
The CIA is being investigated over the deletion of interrogation tapes
One of the detainees in the deleted footage, filmed in 2002, is understood to be Abu Zubaydah, the man referred to by Mr Kiriakou.
The Palestinian was captured in Pakistan in 2002 and sent to Guantanamo Bay, Cuba.
The CIA says it destroyed the tapes to protect the identity of its agents.
But Democrats have accused the agency of a cover-up to hide evidence of possible detainee torture.
The administration of US President George W Bush has always maintained it does not allow the use of torture.