The Justice Department won't try to prevent Congress from granting immunity to a former department official to testify about the firing of federal prosecutors.

The decision all but guarantees that former White House liaison Monica Goodling will be ordered to tell Congress whether she or other Justice officials played politics when hiring and firing prosecutors.

In a letter to House Judiciary Committee Chairman John Conyers, D-Mich., officials from two Justice Department offices investigating the firings said they would prefer not to see an immunity deal because Goodling is a subject of that investigation.

"However, we understand the committee's interest in obtaining Ms. Goodling's testimony," the letter said. "Therefore, after balancing the significant public interest against the impact of the committee's actions on our ongoing investigation, we will not raise an objection or seek a deferral."

The letter was signed by Inspector General Glenn Fine and H. Marshall Jarrett, counsel to the Office of Professional Responsibility.

Committee lawyers must now send an immunity request to a federal judge for approval. Once that deal is approved, Goodling would face a contempt order if she refused to testify. Her lawyer, John M. Dowd, said Monday she would testify under such a deal.

"She'll be honest and clear and she'll work very hard to answer all questions," Dowd said.

Democrats want to know whether U.S. attorneys -- presidential appointees who serve as the top federal law enforcement officials in their state districts -- were fired for political reasons.

The internal Justice Department investigation is also looking at whether Goodling used political affiliations in deciding whom to hire as career prosecutors. Such consideration would be a violation of federal law.

"I believe obtaining her testimony will be a critical step in our efforts to get to the truth about the circumstances surrounding the U.S. attorney firings and possible politicization in the department's prosecutorial function," Conyers said. "The committee will be moving expeditiously to apply for the court order so that we can schedule a hearing promptly."