CIA Director John Brennan has admitted some agency officers used "abhorrent" methods on detainees captured following the 9/11 attacks.
He also said it was "unknowable" whether so-called enhanced interrogation techniques yielded useful intelligence.
With his agency under fire in the aftermath of a US Senate report detailing the CIA's use of torture on detainees after the attacks, Mr Brennan rejected the report's conclusion that the agency had deceived the White House, Congress and the public about its interrogation programme.
"Our reviews indicate that the detention and interrogation programme produced useful intelligence that helped the United States thwart attack plans, capture terrorists and save lives," Mr Brennan told a news conference at the agency's Virginia headquarters tonight.
"But let me be clear. We have not concluded that it was the use of EITs (enhanced interrogation techniques) within that programme that allowed us to obtain useful information from detainees subjected to them," he said.
"The cause-and-effect relationship between the use of EITs and useful information subsequently provided by the detainee is, in my view, unknowable," he added.
The Senate Intelligence Committee on Tuesday published the report of a five-year investigation which found that the CIA misled the White House and the public about its interrogation programme and acted more brutally and pervasively than it acknowledged.
"In a limited number of cases, agency officers used interrogation techniques that had not been authorised, were abhorrent and rightly should be repudiated by all. And we fell short when it came to holding some officers accountable for their mistakes," Mr Brennan said.
But the CIA chief said the "overwhelming majority of officers involved carried out their responsibilities faithfully and in accordance with the legal and policy guidance they were provided."
The Senate committee concluded that the agency failed to disrupt a single plot despite torturing al-Qaeda and other captives in secret facilities worldwide between 2002 and 2006, when George W Bush was president.
Asked whether, as the report asserted, there could have been more than the three detainees the CIA had earlier acknowledged were subjected to simulated drowning or ‘waterboarding’, Mr Brennan said that based on everything he had seen and read it was only those three.
He noted that the CIA was directed by President Bush to carry out a programme to detain terrorism suspects around the world after the 2001 attacks. "In many respects, the programme was uncharted territory for the CIA and we were not prepared," he said.
Asked whether he considered some of the methods used by CIA interrogators to be torture, Mr Brennan said he would leave it to others to place labels on what occurred.
Mr Brennan said he tended to believe that the use of "coercive methods has a strong prospect for resulting in false information" because the detainee may say anything simply to get the methods to stop.
"And I think this agency has said that individuals who were subjected to those techniques provided useful information as well as false information," he added.
Mr Brennan said the CIA believes that information gained from detainees subjected to enhanced interrogation helped locate al-Qaeda chief Osama bin Laden, killed in a US raid in Pakistan in 2011.
But he conceded it was unclear whether the intelligence could have been obtained without using such methods.
Some captives were deprived of sleep for up to 180 hours, at times with their hands shackled above their heads, and the report recorded cases of waterboarding and sexual abuse, including "rectal feeding" or "rectal hydration" without any documented medical need.
Mr Brennan said he believed that "effective, non-coercive methods are available to elicit" useful information from detainees - "methods that do not have a counter-productive impact on our national security and on our international standing".
He said he supported President Barack Obama's 2009 decision to bar the use of these enhanced techniques.
Mr Brennan said it was "lamentable" that the Senate committee did not question CIA officers involved with the interrogations and that the committee failed to reach a bi-partisan consensus on the report.
Committee Democrats issued the report without the support of the panel's minority Republicans.
Earlier, former US vice president Dick Cheney has blasted the Senate report detailing torture of "war on terror" detainees, calling it "terrible" and "full of crap".
Mr Cheney, who was vice president under George W Bush when the brutal "enhanced interrogation techniques" were used, said the programme was entirely justified.
"We did exactly what needed to be done in order to catch those who were guilty on 9/11 and to prevent a further attack, and we were successful on both parts," he told Fox News.