Senate Intelligence Committee Chair Sen. Dianne Feinstein, D-Calif. is surrounded by reporters on Capitol Hill in Washington, Tuesday, Dec. 9, 2014, as she leaves the Senate chamber after releasing a report on the CIA's harsh interrogation techniques at secret overseas facilities. Feinstein branded the findings a "stain on the nation's history." (AP Photo/J. Scott Applewhite)

WASHINGTON - The outgoing U.S Senate Intelligence Committee chairman stood grim-faced, moving through the stark reality of a CIA program she called a "stain on our values and on our history."

Presenting her hotly contested report into CIA torture, Sen Dianne Feinstein sought to lay out her case in the same methodical manner she said guided five years of investigation. Keeping her emotions in check, she avoided invoking her personal dispute with the CIA's director over the agency's monitoring of her investigators.

Feinstein said the conclusions of her report "give me no pleasure."

For the California Democrat, it was her highest profile speech on the Senate floor since revealing nine months ago a dramatic deterioration in relations between her panel's investigators and the top U.S. spy agency. The CIA at the time was asking the Justice Department to launch a criminal probe of Feinstein's staffers, a move she deemed tantamount to a constitutional breach of Congress' right to legislative oversight. The CIA's chief would later apologize, but on Tuesday Feinstein focused on the facts.

Proceeding point by point, she spent almost an hour citing examples of what she described as the CIA torturing al-Qaida prisoners after the Sept. 11, 2001, attacks, and deceiving the nation and the world on the counterterrorism successes its "enhanced interrogation techniques" made possible.

About dozen fellow Democratic senators watched on. Only one Republican, a dissenter, Sen. Dan Coats, was present, until Sen. John McCain entered the Senate to support Feinstein.

"The truth is sometimes a hard pill to swallow," said McCain, who himself was tortured as a prisoner during the Vietnam War. "But the American people are entitled to it nonetheless."

Feinstein's overall summation was stark: Harsh interrogations didn't work and the tactics were "far more brutal than people were led to believe." Releasing just the summary and conclusions of the still secret, 6,700-page report, she said, is a step toward restoring U.S. values.

"America is big enough to admit when it's wrong and confident enough to learn from its mistakes," said Feinstein, who next month will cede control of the committee she has led for the last six years as Republicans assume the Senate majority.

And at 81, and with her political future uncertain, the report could serve as the magnus opus of a five-decade political career that saw Feinstein rise from mayor of San Francisco to one of the dominant Democrats in Congress. She is up for a sixth term as senator in 2018.

The study worked its way through more than 6 million pages of documents. It will incorporate a lengthy Republican rebuttal saying Democrats cherry-picked supporting evidence to reach a pre-determined conclusion of wrongdoing under the administration of President George W. Bush.

President Barack Obama outlawed the enhanced interrogations upon taking office.

The CIA, especially former officials involved in the program, fiercely opposes many of the conclusions reached by Feinstein's investigation.

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Associated Press writer Nancy Benac contributed to this report.

News from © The Associated Press, 2014