(CNN) Sen. Dianne Feinstein on Thursday called on the CIA to declassify documents that detail the role that Gina Haspel, President Donald Trump's pick to be CIA director, played in the George W. Bush administration's interrogation and detention program.

Feinstein sent a letter to Haspel and outgoing CIA Director Mike Pompeo saying that a full accounting of Haspel's record in the Bush-era interrogation program is needed to evaluate her record.

"As we move forward with the nomination process for Ms. Haspel, my fellow senators and I must have the complete picture of Ms. Haspel's involvement in the program in order to fully and fairly review her record and qualifications," Feinstein wrote. "I also believe the American people deserve to know the actual role the person nominated to be the director of the CIA played in what I consider to be one of the darkest chapters in American history."

Gina Haspel, CIA deputy director and President Donald Trump's nominee to lead the agency

Feinstein is poised to play a key role in the confirmation process. She was chairwoman of the Senate Intelligence Committee when Democrats released their scathing report on the Bush-era interrogation program and is still on the panel

After Haspel was nominated, Feinstein praised her record as deputy CIA director, and said the two of them have had lengthy conversations about the CIA's treatment of terror suspects. But Feinstein, who is up for re-election this year and faces a challenger from her left , said she would wait until after Haspel's confirmation hearing to decide how she'll vote on her confirmation.

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