(CNN) -- Sen. Dianne Feinstein on Friday toughened her stance against Gina Haspel, President Donald Trump's pick to be CIA director, saying she was "very wary" of promoting someone to run the agency who was involved in the George W. Bush administration's controversial CIA detention and interrogation program.
"To promote someone so heavily involved in the torture program to the top position at the CIA, the agency responsible for one of the darkest chapters in our history, is a move that I'm very wary of," the California Democrat said in a statement.
The California Democrat's statement Friday struck a markedly different tone than her initial comments praising Haspel, who is currently the deputy CIA director and, if confirmed, would be the first woman to run the agency.
It's a sign that Feinstein, who is facing a challenger from her left in her reelection campaign, looks less likely to back Haspel's confirmation.
Haspel, who has spent 33 years in the CIA, was in charge of a "black site" in Thailand in 2002 during the harsh interrogations of detainees, although she was not in charge when al Qaeda suspect Abu Zubaydah was waterboarded at least 83 times.
Haspel was also chief of staff for Jose Rodriguez, director of the CIA's National Clandestine Service, when he ordered the destruction of recordings of CIA interrogations in 2005.
Those episodes have stirred up opposition to Haspel among some Democrats and at least one Republican, and the Trump administration is gearing up for a bruising confirmation battle.
Sen. John McCain, who was tortured as a prisoner of war in Vietnam, sent Haspel a letter Friday demanding she detail her role in detainee interrogations and the destruction of the CIA tapes, as well as asking whether she was ever "in a position of authority to stop, or prevent the future employment of 'enhanced interrogation techniques.'"
McCain is an important voice for Republicans, even with his absence from Washington while he battles cancer, and Feinstein could become a key vote for Democrats.
As chairwoman of the Senate Intelligence Committee from 2009 through 2014, Feinstein spearheaded the panel's scathing 6,700-page report on the Bush-era interrogation program, which concluded that the use of tactics like waterboarding was not effective at obtaining accurate information or gaining cooperation from detainees.
But when Haspel was picked to succeed Mike Pompeo as CIA director earlier this month, Feinstein praised Haspel's record in her year as deputy director and said the two have discussed the issue of torture at length.
"I have spent some time with her," Feinstein said at the time. "We have had dinner together. We have talked. Everything I know is that she has been a good deputy director of the CIA."
Her comments sparked criticism from the left, including from her opponent within her own party Kevin de León.
"This should be an easy call. Not only should she be a NO vote on Trump's CIA pick, she should also be a leading voice rallying all Dems against this nomination," de León tweeted.
The White House has also pointed to Feinstein's remarks, with press secretary Sarah Sanders suggesting during a briefing last week that Feinstein backed Haspel's nomination, though she quickly corrected herself.
Last week, Feinstein sent a letter to the CIA demanding the declassification of Haspel's records. And in her statement Friday, Feinstein specified there was a difference between praising Haspel's record as deputy director and supporting her to run the CIA.
"Her experience may have served her well as deputy, but the top position is another matter entirely," Feinstein said.
© Copyright 2018 CNN. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.
for more features.