In a letter to Obama at that time, Brennan said he was "a strong opponent of many of the policies of the Bush administration, such as the pre-emptive war in Iraq and coercive interrogation tactics, to include waterboarding."

White House officials say they don't expect Brennan to face similar trouble this time around given his four years of service in the Obama administration.

"The issue has been removed from the debate because the president and John Brennan, as his top counterterrorism adviser, brought those techniques to an end," said Ben Rhodes, Obama's deputy national security adviser.

But some lawmakers and outside groups aren't as easily convinced. Sen. John McCain, R-Ariz., issued a statement about Brennan saying he had "many questions and concerns about his nomination to be director of the Central Intelligence Agency, especially what role he played in the so-called enhanced interrogation programs while serving at the CIA during the last administration, as well as his public defense of those programs."

Brennan's nomination will also put a spotlight on the administration's controversial drone program. He was the first Obama administration official to publicly acknowledge the highly secretive targeted killing operations, defending the legality of the overseas program and crediting it with protecting American lives and preventing potential terror attacks.

The American Civil Liberties Union voiced its concerns over Brennan's nomination Monday, saying the Senate should not move forward until it is clear the nominee "will end its targeted killing program."

Brennan would replace Michael Morell, the CIA's deputy director who has been acting director since David Petraeus resigned in November after admitting to an affair with his biographer. Hagel would replace retiring Pentagon chief Leon Panetta.

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Associated Press writers Donna Cassata and Tom Raum contributed to this report.

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Follow Julie Pace at http://twitter.com/jpaceDC