CIA Director John Brennan on Thursday delivered a lengthy and detailed defense of his agency's post-9/11 interrogation techniques, reminding the nation that agents used the tactics in pursuit of a single goal -- preventing another devastating terror attack.

"[CIA officers] did what they were asked to do in the service of our nation," Brennan said, in his first public response to a controversial report issued earlier this week by Senate Democrats.

The director, who was a top official within the spy agency under the George W. Bush administration when the interrogation tactics were used, disputed key findings in the report -- which claimed the "enhanced" tactics were not effective and accused the agency of misleading Congress.

Brennan claimed that detainees subjected to harsh methods produced "very useful, valuable intelligence." Whether that information could have been obtained with other methods, he said, is "unknowable."

He also said "the record simply does not support" the suggestion the agency intentionally misled officials about the program.

Further, Brennan said one of the most "frustrating" aspects of the report is it paints a picture of CIA officers as "untrustworthy."

"This in no way comports with my experience in the CIA," he said, during a rare press conference.

Brennan's response comes after several former Bush administration officials -- including ex-CIA Director Michael Hayden and former Vice President Dick Cheney -- have blasted the report as biased and inaccurate. In an interview Wednesday with Fox News, Cheney called it "deeply flawed."

Brennan conceded Thursday that some aspects of the report were "sound and consistent" with their own findings. He said the agency was "unprepared" to launch the program and in some cases, officers used unauthorized and "abhorrent" techniques. He said he supported President Obama's decision to end "enhanced" techniques like waterboarding.

But he also lamented that the Senate intelligence committee did not interview CIA officers for its investigation. And he stressed that the agency's interrogation program was mostly conducted in accordance with legal guidance at the time. He tried to remind the nation that they were doing their best to protect Americans from another 9/11-style attack, recounting the fear that struck the nation that day.

"Never again, we vowed -- never again," Brennan said. "Al Qaeda was poised, ready and prepared to pursue its violent agenda."

This, he said, was the "backdrop" for the program. "There were no easy answers," Brennan said.

As Brennan spoke, intelligence committee Chairwoman Sen. Dianne Feinstein, D-Calif., who released the report, tried to rebut his comments on Twitter. She tweeted, "Covert authority did not include authorization to use coercive interrogation techniques," and tweeted that the techniques "don't work."

The release of the report on Tuesday touched off a furious debate in Washington and across the country about the morality and effectiveness of CIA interrogation techniques from the Bush era -- as well as the potential risk of the report's release triggering a backlash against Americans at home and abroad.

The White House and Obama backed the decision to release the report, despite warnings from lawmakers and some inside the administration that it could lead to reprisals.