John Brennan, President Barack Obama's choice for director of central intelligence, is to go before the Senate Select Committee on Intelligence at 2:30 p.m. Thursday for a confirmation hearing.

Brennan, a 25-year CIA veteran, began advising the president during his 2008 campaign. Brennan’s nomination is expected to be a controversial one, because four years ago he withdrew his name from consideration for the CIA director’s spot after critics tried to connect him with questionable interrogation practices, such as waterboarding, during the George W. Bush presidency.

The 57-year old, who was appointed deputy national security adviser for homeland security and counterterrorism in 2009, has said those practices, generally considered torture, won’t happen again. However, Brennan defended the controversial use of drone strikes last April, and admitted that noncombatants were sometimes killed.

“Unfortunately, in war, there are casualties, including among the civilian population,” Brennan said on ABC's “This Week.” “We’ve done everything possible in Afghanistan and other areas to reduce any risk to that civilian population. Unfortunately, al Qaeda burrows within these areas, you know, safe havens as well as areas where there are civilians, but we’ve been very, very judicious in working with our partners to try to be surgical in terms of addressing those terrorist threats.”

Brennan also said that “sometimes you have to take life to save lives, and that’s what we’ve been able to do to prevent these individual terrorists from carrying out their murderous attacks.”

These controversies flared up again after the revelation on Wednesday of a secret CIA drone base in Saudi Arabia. In addition to that, a report from NBC News revealed a secret Justice Department 16-page memo containing the legal rationale for the government's authority to order the deaths of American citizens believed to be "senior operational leaders" of al Qaeda or its affiliates. 

Obama has agreed to Congress' intelligence committees viewing the classified memo that provides reasons for such attacks, multiple news sources reported last night.

Sen. Dianne Feinstein, D-Calif., who chairs the Intelligence Committee, has indicated support for Brennan. However, her  staffers told The Associated Press that the senator and Republicans will be asking Brennan to explain the interrogation program, how much useful intelligence it has obtained, and when.

But it isn’t only Feinstein who will be tackling Brennan. Other Democrats, like Sen. Mark Udall of Colorado, last week expressed disappointment in the nominee for not being prepared to discuss the committee’s recent report on the CIA's Detention and Interrogation Program.

Udall and Sens. Carl Levin, D-Mich., and Ron Wyden, D-Ore., met with Brennan last Wednesday to review the findings, which were based on a review of millions of pages of CIA records that raised questions about operations and oversight.

“Not only was he not prepared to discuss the important findings, but he hadn’t reviewed the report at all,” Udall said in a statement, noting Brennan promised to do the review before the confirmation hearing. “I intend to hold him to that promise, and I hope Mr. Brennan will be more forthcoming in his testimony. I understand that he may not see it in his or the CIA’s interests to criticize the very agency that he hopes to lead, but I see this as an opportunity for Mr. Brennan to correct the record, institute the necessary reforms and help restore the CIA's reputation for integrity and analytical rigor.”