WASHINGTON — CIA Director-designate John Brennan's vigorous defense of drone strikes to kill terror suspects – even American citizens – overseas is causing key lawmakers to consider lifting secrecy from what has become an important weapon in the fight against al-Qaida.

Brennan, President Barack Obama's top counterterror adviser, was grilled for more than three hours Thursday before the Senate Intelligence Committee on the drone program he leads, as well as on the CIA's harsh interrogation techniques during the Bush administration, which he denounced, and on leaks of classified information to the media, which Brennan vehemently denied being a part of.

Despite Brennan's wide-ranging testimony and the White House's release of a top secret memo explaining its legal rationale for the strikes just hours before the confirmation hearing began, some senators said afterward it was time to bring the drone program into the open.

In a hearing that was interrupted by anti-drone protests that brought it to a brief halt and forced Capitol Hill security to empty the room of all but credentialed staff and media, Brennan told the committee that missile strikes by the unmanned drones are used only against targets planning to carry out attacks against the United States, never as retribution for an earlier one.

"Nothing could be further from the truth," he declared.

Referring to one American citizen killed by a drone in Yemen in 2011, he said Anwar al-Awlaki had ties to at least three attacks planned or carried out on U.S. soil. They included the Fort Hood, Texas, shooting that claimed 13 lives in 2009, a failed attempt to down a Detroit-bound airliner the same year and a thwarted plot to bomb cargo planes in 2010.

"He was intimately involved in activities to kill innocent men, women and children, mostly Americans," Brennan said.

The committee's chairwoman, Sen. Dianne Feinstein, D-Calif., told reporters after the hearing that she wanted to open more of the program to the public so U.S. officials can acknowledge the strikes and correct what she said were exaggerated reports of civilian casualties.

Feinstein said she and other senators were considering legislation to set up a special court system to regulate drone strikes, similar to the one that signs off on government surveillance in espionage and terrorism cases.

Speaking with uncharacteristic openness about the classified program, Feinstein said that the CIA had allowed her staff to make more than 30 visits to the agency's northern Virginia headquarters to monitor strikes but that such transparency needed to be increased. Her comments came after the White House, under pressure from the committee, gave senators on the panel a Justice Department memo outlining the legal justification for drone strikes. But senators complained that aides weren't allowed to see it.

"I think the process set up internally is a solid process," Feinstein said of the methods used to decide when to launch drones and against whom, but added: "I think there's an absence of knowing exactly who is responsible for what decision. So I think we need to look at this whole process and figure a way to make it transparent and identifiable."

Feinstein said other senators including Dick Durbin, D-Ill., Chuck Grassley, R-Iowa, and Pat Leahy, D-Vt., have all indicated "concern and interest" over how to regulate drones.

Rep. Adam Schiff, D-Calif., a member of the House Intelligence Committee, said some members of his panel also had been looking at establishing a "court-like entity" to review the strikes.

"I think the House and Senate ought to put their heads together and come up with some way to require, either initially or after the fact, a review of an operation when it takes the life of an American citizen," Schiff said.

In a long afternoon in the witness chair, Brennan was questioned on other issues, such as the use of waterboarding and other interrogation techniques during the George W. Bush administration. He declined to say whether he believes waterboarding, which simulates drowning, amounted to torture, but he said firmly it was "something that is reprehensible and should never be done again."

Brennan, 57, is a veteran of more than three decades in intelligence work. He withdrew his name from nomination to head the CIA four years ago amid questions about the role he played at the CIA when the Bush administration approved waterboarding and other forms of "enhanced interrogation" of suspected terrorists.

On the question of waterboarding, Brennan said that while serving as a deputy manager at the CIA during the Bush administration, he was told such interrogation methods produced "valuable information." Now, after reading a 300-page summary of a 6,000-page report on CIA interrogation and detention policies, he said he does "not know what the truth is."

Brennan bristled once during the day, when he was questioned about leaks to the media about an al-Qaida plot to detonate a new type of underwear bomb on a Western airline.

Sen. James Risch, R-Idaho, accused him of having leaked classified information in a telephone call with former government officials who were preparing to make television appearances to explain the plot.

"I disagree with that vehemently," the nominee shot back.

On May 7 of last year, The Associated Press reported that the CIA thwarted an ambitious plot by al-Qaida's affiliate in Yemen to destroy a U.S.-bound airliner, using a bomb with a sophisticated new design. The bombing would have taken place near the anniversary of the killing by U.S. Navy SEALs of Osama bin Laden. The next day, the Los Angeles Times was the first to report that the would-be bomber was cooperating with U.S. authorities.

Risch and Sen. Dan Coats, R-Ind., were among those who contended Brennan inadvertently had revealed that the U.S. had a spy inside Yemen's al-Qaida branch when, hours after the first AP report appeared, he told a group of media consultants that "there was no active threat during the bin Laden anniversary because ... we had inside control of the plot."

Brennan won praise from several members of the committee as the day's proceedings drew to a close.

"I think you're the guy for the job, and the only guy for the job," said Sen. Jay Rockefeller, D-W.Va.

The panel will meet in closed session next week to discuss classified material.

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Associated Press writers Julie Pace, Lara Jakes, Donna Cassata and David Espo contributed to this report.

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Follow Kimberly Dozier on Twitter: http://twitter.com/KimberlyDozier

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