US national intelligence chief Mike McConnell has said the interrogation technique of water-boarding "would be torture" if he were subjected to it.
Mr McConnell said the legal test for torture should be "pretty simple"
Mr McConnell said it would also be torture if water-boarding, which involves simulated drowning, resulted in water entering a detainee's lungs.
He told the New Yorker there would be a "huge penalty" for anyone using it if it was ever determined to be torture.
The US attorney-general has declined to rule on whether the method is torture.
However, Michael Mukasey said during his Senate confirmation hearing that water-boarding was "repugnant to me" and that he would institute a review.
In December, the House of Representatives approved a bill that would ban the CIA from using harsh interrogation techniques such as water-boarding.
President George W Bush has threatened to veto the bill, which would require the agency to follow the rules adopted by the US Army and abide by the Geneva Conventions, if the Senate passes it.
In the interview with the New Yorker, the US Director of National Intelligence said he would regard water-boarding as torture if it was used against him.
The controversial technique involves a prisoner being stretched on his back, having a cloth pushed into his mouth and/or plastic film placed over his face and having water poured onto his face. He gags almost immediately.
"If I had water draining into my nose, oh God, I just can't imagine how painful!" he told the magazine.
"Whether it's torture by anybody else's definition, for me it would be torture."
Mr McConnell said the legal test for torture should be "pretty simple".
"Is it excruciatingly painful to the point of forcing someone to say something because of the pain?" he added.
But the retired vice-admiral declined for legal reasons to say whether the technique should be considered torture by the US government.
"If it ever is determined to be torture, there will be a huge penalty to be paid for anyone engaging in it," he said.
CIA officials have been quoted as saying that water-boarding has been used on three prisoners since 2001, including al-Qaeda recruiter Abu Zubaydah, but on nobody since 2003.
In July 2007, President Bush signed a controversial executive order on the treatment of suspects detained by the CIA which did not outlaw the agency's use of "enhanced interrogation techniques" such as water-boarding.