He said he had no problems even if CIA interrogators went beyond their brief to defend the nation.

Asked about reports that the CIA ran a secret programme from 2004 to hire contractors to kill Al-Qaeda operatives without informing Congress, Cheney said: 'The direction was for them not to tell Congress until certain lines were passed, until the programme became operational.''

Speaking on CBS's 'Face the Nation', McCain too said it was a wrong move which will effect the morale of the agency. With the Obama administration announcing the probe, a number of CIA officials have put off plans to retire or leave the agency so that they can maintain their access to classified files and be in a better position to defend themselves.

'Once you're out, it gets a lot harder,'' a retired CIA official was quoted as saying recently.

The investigation is likely deepen the wedge between the CIA and the Justice Department which have a fractious history.