By Evan Perez, CNN Justice Reporter
A new congressional fight is brewing over the Central Intelligence Agency's controversial use of harsh interrogations almost decade ago.
Sen. Mark Udall, D-Colorado, is threatening to block the nomination of President Barack Obama's choice for CIA general counsel unless the agency provides an internal report that he says bolsters findings made by a congressional investigation of the interrogation program.
The Senate Intelligence Committee produced a 6,300-page report on the program, which used methods such as waterboarding on prisoners held by the CIA in the years after the September 11, 2001, terrorist attacks.
The Senate report is highly critical of the program and found it produced little intelligence value, according to people familiar with the findings. But it has not been released publicly because the CIA has officially disputed its conclusions.
At a hearing Tuesday on the nomination of Caroline Krass, who would be the agency's top lawyer, Udall said former CIA Director Leon Panetta initiated the agency's own internal study of the program. That internal probe, Udall believes, has reached conclusions similar to those found by the Senate committee and contradicts the CIA's official denials. He says he and other lawmakers on the committee asked the CIA for the internal report, but the agency has yet to produce it.
"It raises fundamental questions about why a review the CIA conducted internally years ago ... is so different from the CIA's formal written response to the committee study," Udall said.
The Senate report was completed a year ago. Some critics of the report say it has errors and is poorly written, making some of its findings hard to understand.
But the CIA has also come under fire for refusing to provide additional information to fully explain the program. The CIA had the legal backing of Justice Department memos at the time, but the methods used were called torture by Obama and Attorney General Eric Holder.
CIA spokesman Dean Boyd said: "We're aware of the Committee's request and will respond appropriately."
Krass, a former lawyer in the Justice Department's Office of Legal Counsel and in the Obama White House, resisted making promises to provide more information to the Senate committee to complete its work on the CIA program.
In response to questions from Sen. Dianne Feinstein, D-California, who heads the Senate Intelligence panel, Krass said she would make sure lawmakers understood the executive branch's decisions, but wouldn't support releasing all Office of Legal Counsel memos as requested by congress.
"The OLC opinions represent pre-decisional confidential legal advice that's been provided, and protecting the confidentiality of that legal advice preserves space for there to be a full and frank discussion amongst clients and the policy makers and their lawyers within the executive branch and I believe furthers, really furthers the rule of law because it allows for the effective functioning of the executive branch," Krass said.