CIA director John Brennan has defended his agency from accusations in a Senate report that it used inhumane interrogation techniques against terrorist suspects with no security benefits to the US.
Mr Brennan opened a rare news conference by recounting the horrors of the September 11 2001 terrorist attacks, his agency's determination to prevent another such assault and the fact that CIA officers were the first to fight and early to die in the Afghanistan war.
He conceded unauthorised and in some cases abhorrent methods were used against captives.
But Mr Brennan asserted the CIA "did a lot of things right" at a time when there were "no easy answers".
The Senate torture report this week asserted that none of the CIA's techniques used against captives provided critical, life-saving intelligence.
Mr Brennan said that valuable intelligence did come from the interrogations but conceded that it is impossible to know whether the detainees provided that information because of the "enhanced interrogation techniques".
He said the cause-and-effect relationship is "unknown and unknowable." In that respect, he stopped short of the claims of other defenders of the programme who said the tough methods saved thousands of American lives.
Mr Brennan would not say whether he considered some of the techniques torture.
Mr Brennan's remarks were part of a campaign by the CIA and several of its past leaders to discredit a five-year Senate investigation into the CIA's interrogation practices after 9/11, concerned that the historical record may define them as torturers instead of patriots and expose them to legal action around the world.
The Senate intelligence committee's report does not urge prosecution for wrongdoing, and the Justice Department has no interest in reopening a criminal probe.
But the threat to former interrogators and their superiors was underlined as a UN special investigator demanded those responsible for "systematic crimes" be brought to justice, and human rights groups pushed for the arrest of key CIA and Bush administration figures if they travel overseas.
Current and former CIA officials have pushed back, determined to paint the Senate report as a political stunt by Senate Democrats tarnishing a programme that saved American lives.
It is a "one-sided study marred by errors of fact and interpretation - essentially a poorly done and partisan attack on the agency that has done the most to protect America," former CIA directors George Tenet, Porter Goss and Michael Hayden wrote in a Wall Street Journal opinion piece.
Mr Hayden was singled out by Senate investigators for what they said was a string of misleading or outright false statements he gave in 2007 about the importance of the CIA's brutal treatment of detainees in thwarting terrorist attacks.
He described the focus on him as "ironic on so many levels" as any wrongdoing pre-dated his arrival at the CIA. "They were far too interested in yelling at me," Mr Hayden said.
The intelligence committee's 500-page release concluded that the CIA inflicted suffering on al Qaida prisoners beyond its legal authority and that none of the agency's "enhanced interrogations" provided critical, life-saving intelligence. It cited the CIA's own records, documenting in detail how waterboarding and lesser-known techniques such as "rectal feeding" were actually employed.
The CIA is now in the uncomfortable position of defending itself publicly, given its basic mission to protect the country secretly. Its 136-page rebuttal suggests Senate Democrats searched through millions of documents to pull out only the evidence backing up predetermined conclusions. "That's like doing a crossword puzzle on Tuesday with Wednesday's answer's key," the CIA said.
Challenging one of the report's most explosive arguments - that harsh interrogation techniques did not lead to Osama bin Laden - the CIA pointed to questioning of Ammar al-Baluchi, who revealed how an al Qaida operative relayed messages to and from bin Laden after he departed Afghanistan.
Before then, the CIA said, it only knew that courier Abu Ahmad al-Kuwaiti interacted with bin Laden in 2001 when the al Qaida leader was accessible to many of his followers. Al-Kuwaiti eventually led the US to bin Laden's compound in Pakistan.
Poring over the same body of evidence as the investigators, the CIA insisted most of the 20 case studies cited in the Senate report actually illustrated how enhanced interrogations helped disrupt plots, capture terrorists and prevent another 9/11-type attack.
The agency said it obtained legal authority for its actions from the Justice Department and White House, and made "good faith" efforts to keep congressional leaders informed.