CIA boss John Brennan defends post 9/11 strategy, CIA Director John Brennan has said some of the agency's interrogation methods after 9/11 were "abhorrent".
But he said overall the interrogation programme implemented after 9/11 yielded information that saved lives.
A scathing Senate report said "brutal" methods like waterboarding and sleep deprivation were ineffective.
Speaking at CIA headquarters, Mr Brennan admitted some officers acted beyond their authority and should have been held accountable.
But he asserted the CIA "did a lot of things right" in a time when there were "no easy answers" and there were fears of more attacks from al-Qaeda.
While he was speaking, Senator Dianne Feinstein, who heads the committee that produced the report, was rejecting his arguments on Twitter.
One tweet said: "Brennan: 'unknowable' if we could have gotten the intel other ways. Study shows it IS knowable: CIA had info before torture. #ReadTheReport"
Mr Brennan was a senior CIA official in 2002 when the detention and interrogation programme was put in place.An outgoing Democratic Senator, Mark Udall, has called on Mr Brennan to quit, citing interference from the CIA in preparing the report.
A summary of the larger classified report says that the CIA carried out "brutal" and "ineffective" interrogations of al-Qaeda suspects in the years after the 9/11 attacks on the US and misled other officials about what it was doing.
The information the CIA collected using "enhanced interrogation techniques" failed to secure information that foiled any threats, the report said.
The UN and human rights groups have called for the prosecution of US officials involved in the 2001-2007 programme."As a matter of international law, the US is legally obliged to bring those responsible to justice," Ben Emmerson, UN Special Rapporteur on Human Rights and Counter-Terrorism, said in a statement made from Geneva.
He said there had been a "clear policy orchestrated at a high level".
The chances of prosecuting members of the Bush administration are unlikely - the US justice department has pursued two investigations into mistreatment of detainees and found insufficient evidence.
On Wednesday, an unnamed justice department official told the Los Angeles Times prosecutors had read the report and "did not find any new information" to reopen the investigation.
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