US national intelligence chief Mike McConnell has said the interrogation technique of water-boarding "would be torture" if he was subjected to it.

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.