(CNN) Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, said Monday it was "unacceptable" how little material about CIA director nominee Gina Haspel has been made public, while the CIA provided the Senate with a new batch of classified materials related to Haspel's record.

Warner on Monday wrote a letter to Haspel, obtained by CNN, saying that the CIA has failed to make enough of Haspel's record public — and he urged Haspel, currently acting CIA director, to intervene herself to declassify additional materials.

"Given that we are only two days from the date of your confirmation hearing on May 9, 2018, this lack of transparency for the American people about someone nominated for a cabinet-level position is unacceptable," Warner wrote. "As the acting Director of the CIA, it is in your power to order the declassification of relevant material or to hasten the process. I urge you to take immediate action to remedy these problems."

Warner's letter and the additional classified documents come ahead of Haspel's Wednesday confirmation hearing, in which Haspel's performance may determine whether she can secure enough votes to be confirmed as the first female director at Langley. Haspel has spent most of her 33-year CIA career undercover, and her role in the George W. Bush administration interrogation and detention program has generated significant opposition to her selection

Republicans control 51 seats in the Senate, but at least one GOP member -- Sen. Rand Paul of Kentucky -- has said he plans to vote against Haspel . Arizona Republican Sen. John McCain is recovering from cancer treatment in his home state, and, as someone who himself was tortured while he was a prisoner war, is among the most passionate advocates against torture in Congress.

"The torture of detainees in US custody during the last decade was one of the darkest chapters in American history. Ms. Haspel needs to explain the nature and extent of her involvement in the CIA's interrogation program during the confirmation process," McCain said in a statement shortly after her nomination was announced

This means Haspel will likely need support of at least a few Democrats in order to be confirmed.

Many Democrats have signaled they'll wait for Wednesday's hearing before weighing in -- at least publicly. On Monday evening, West Virginia Democratic Sen. Joe Manchin, a swing vote who sits on the Senate Intelligence Committee, made his clearest indication yet in an interview with CNN that he could support Haspel, calling her a "true soldier" and someone who has "done her job."

Warner's letter was sent to Haspel the same day that the CIA provided two boxes of classified documents to the Senate about her career.

CIA spokesman Ryan Trapani said the documents "cover the entirety of her career, including her time in CIA's Counter Terrorism Center in the years after 9/11."

Officials dropped two cardboard boxes that said "HAND CARRY" written by a felt-tip marker; one box went to the Senate Intelligence Committee, and the other to the Senate's security office.

On Friday, Haspel offered to withdraw her nomination after some White House officials raised concerns with her ability to get confirmed, but the White House and Haspel are moving forward with her confirmation. President Donald Trump defended Haspel in a tweet Monday morning and White House press secretary Sarah Sanders said Haspel is "100%" committed to seeing her confirmation process through.

A group of Democrats on the Senate Intelligence Committee, including Sens. Dianne Feinstein of California, Ron Wyden of Oregon and Martin Heinrich of New Mexico, have repeatedly demanded that the CIA make public Haspel's record as the supervisor of a CIA "black site" in Thailand in 2002 where detainees were interrogated, as well as her role in the 2005 destruction of CIA interrogation tapes.

The CIA responded by saying it would provide classified materials for all senators to review, but also that certain materials related to the interrogation program could not be made public for security reasons.

That response has not satisfied Democrats, particularly after the CIA did declassify an internal 2011 report written by then-deputy CIA director Mike Morell that cleared Haspel of wrongdoing over the destruction of CIA interrogation tapes. The senators on Friday asked Director of National Intelligence Dan Coats to declassify information related to Haspel's role in the interrogation program.

Warner has also asked the Justice Department to provide the Senate Intelligence Committee with the full Justice Department report on the tapes incident that was written by the special prosecutor appointed to investigate the matter, who did not bring any charges.

The Justice Department on Monday gave the Senate panel the executive summary of a classified report from the special prosecutor who investigated the 2005 destruction of CIA interrogation tapes.

John Durham, the federal prosecutor who was tapped to investigate the destruction of the tapes in 2008, closed the case in 2010 without bringing any charges. Warner urged the Justice Department last month to provide the Senate with a copy of Durham's classified report, in order to assess Haspel's role in the matter. DOJ provided the executive summary of the report to the intelligence panel, the source said, and it remains classified.

In his Monday letter, Warner wrote that the CIA "has opened itself up" to the criticism that it is only releasing favorable materials while suppressing related items that could reflect negatively.

"While it is certainly complicated to declassify locations and work performed in the field, to date the Agency has not even been able to make public all of the leadership and supervisory positions you held at CIA headquarters," Warner wrote.