(CNN) Former FBI Deputy Director Andrew McCabe has requested the Senate Judiciary Committee provide him with immunity from prosecution in exchange for testifying at an upcoming congressional hearing focused on how senior officials at the FBI and Justice Department handled the investigation of Hillary Clinton's private email server, according to a letter obtained by CNN.

"Under the terms of such a grant of use immunity, no testimony or other information provided by Mr. McCabe could be used against him in a criminal case," wrote Michael Bromwich, a lawyer for McCabe, to Senate Judiciary Chairman Chuck Grassley, who has requested McCabe testify next week.

Grassley, an Iowa Republican, has quietly requested that several former officials appear in front of the Judiciary Committee to discuss the long-awaited internal Justice Department report, which sources say will detail a series of missteps surrounding the Justice Department and FBI's investigation into Clinton's handling of classified information while secretary of state.

The inspector general's report has not yet been released, but Grassley has invited former FBI Director James Comey and former Attorney General Loretta Lynch to testify as well, according to those familiar with the plans.

The stakes for McCabe's appearance, however, are particularly high. The former No. 2 at the FBI is entangled in a separate criminal investigation stemming from an earlier report from the inspector general's office that concluded he lied to internal investigators. McCabe has steadfastly denied wrongdoing, but any congressional testimony he provides could have serious implications for his criminal case.

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