WASHINGTON (CNN) -- Stepping up congressional pressure on Attorney Gen. Alberto Gonzales, the House Judiciary Committee Tuesday issued a subpoena demanding additional internal Justice Department documents relating to the firing of eight federal U.S. attorneys.

House Judiciary Chairman John Conyers, D-Michigan, said in a letter to Gonzales he had been patient over the past few weeks in awaiting a response to its request for additional material, but that the Justice Department had run out of time to voluntarily comply.

"At this point further delay in receiving these materials will not serve any constructive purpose, Conyers said.(Read Conyers' letter to Gonzales [PDF])

Later in the day, Justice Department spokesman Brian Roehrkasse called the move "unfortunate."

"Because there are individual privacy interests implicated by publicly releasing this information it is unfortunate that Congress would choose this option," he said in a statement. "In light of these concerns we will continue to work closely with congressional staff and we still hope and expect that we will be able to reach an accommodation with the Congress."

The subpoena calls for both complete copies of documents previously turned over in redacted form as well as information on certain subjects the Justice Department does not want to turn over, such as ones concerning replacement candidates for the fired U.S. prosecutors as well as those dealing with how DOJ responded to congressional and media inquiries concerning the issue.

The Senate Judiciary Committee has sent the attorney general letters demanding similar releases of documents, but had not used its subpoena authority. The Committee is awaiting Gonzales' much anticipated appearance before the panel next Tuesday.

Gonzales has been devoting much of his schedule to preparing for the hearing, which may determine whether he is able to cling to his position.

The Senate Committee Tuesday broadened its previous demand for documents by asking for all material which involves the prosecution of an aide to Wisconsin's Democratic governor. That prosecution led by the U.S. attorney in Milwaukee was overturned by a federal appeals court for lack of sufficient evidence.

-- CNN Justice Producer Terry Frieden