WASHINGTON (CNN) — The Justice Department's Acting Associate Attorney General withdrew his name from nomination to be confirmed to the third-highest ranking job, saying he believed he would not be confirmed because of the ongoing battle over access to Justice Department documents related to the firing of U.S. attorneys last year.

William Mercer has served in an Acting capacity in the position since last September, but his nomination has been delayed by the Senate Judiciary Committee.

Mercer had been serving in a dual role as Associate Attorney General and U.S. Attorney for Montana–a post he will continue to hold.

"I have concluded that it is highly unlikely that both the Judiciary Committee and the Senate will take prompt action on my nomination in the near term, if ever," Mercer said in a letter to Attorney General Alberto Gonzales, which was released by the Justice Department late Friday.

"This view is informed in part by statements suggesting that some senior Justice nominees will not be voted upon until the Senate receives e-mails and witnesses it has demanded from the White House," Mercer told the Attorney General.

Senior Justice Department officials privately expressed sadness with the move, the latest in a series of announced departures from top Justice Department jobs in the the wake of a controversy over the U.S. attorney firings.

One Justice Department official pointed to an early December e-mail from then chief of staff Kyle Sampson calling for Mercer to be given "a heads up" about the firings as evidence Mercer was totally uninvolved in the controversial dismissals.

Senate Judiciary Committee Chairman Patrick Leahy (D-VT) issued a statement blaming the Justice Department for Mercer's decision.

"The White House has found many ways to keep sunlight from reaching some of the darker corners of the Bush Justice Department, but this is a new once," Leahy said. "With a confirmation hearing looming next Tuesday they have withdreawn this nomination to avoid having to answer more questions under oath," he said.

Although Mercer will remain a Justice Department official in Montana, his departure will add to a hole in top management at the department. The second highest ranking official Deputy Attorney General Paul McNulty has announced he will be leaving this summer.

– CNN Justice Producer Terry Frieden