On the eve of U.S. Attorney Eric H. Holder Jr.'s appearance before Congress, a senior Justice Department official said the department cannot meet the deadline Republican lawmakers have set to turn over more documents on the Fast and Furious gun operation or be held in contempt of Congress.

Deputy Attorney General James M. Cole said that the February 9 deadline to submit all documents on the botched gun operation set this week by Rep. Darrell Issa (R-Calif.), chairman of the Committee on Oversight and Government Reform, was "impossible to meet."

"We will continue in good faith to produce materials, but it simply will not be possible to finish the collection, processing and review of materials by the date sought in your most recent letter," Cole wrote in a five-page letter to Issa on Wednesday.

On Tuesday, Issa threatened to hold Holder in contempt if the Justice Department does not turn over the documents, which the committee subpoenaed in October.

Holder is scheduled to testify before Issa's committee Thursday morning. According to partial testimony released by the Justice Department late Wednesday, Holder is expected to say that the "gunwalking" tactic used in Fast and Furious is "wholly unacceptable,” was used in a "misguided effort" and will not be employed in the future.

Holder is likely to be grilled extensively about the Phoenix operation, in which federal agents targeting a Mexican drug cartel allowed more than 2,000 guns to flow illegally onto U.S. streets and into Mexico between 2009 and January 2011.

The Fast and Furious issue has triggered repeated criticism in the past year from congressional Republicans, and led to the reassignment of the director of the Bureau of Alcohol, Tobacco, Firearms, and Explosives and the departure of the U.S. Attorney in Phoenix, who stepped down amid a shakeup of other top ATF officials. Several Republican lawmakers have called on top Justice officials, including Holder, to resign.

In his letter to Issa, Cole said that the Justice Department had already turned over more than 6,400 pages of material and produced numerous witnesses, including senior-level Justice officials.

The department has created a team of lawyers and technical personnel to collect and process the documents, Cole said. And Holder has appeared five times before a congressional committee in the past year to be questioned about Fast and Furious.

A spokesman for Issa said one point of contention is that the Justice Department will not provide records of internal deliberations that took place after February 4, 2011, the first day that the Justice Department responded to the congressional inquiry.

"The Justice Department is under investigation for both its conduct during Operation Fast and Furious as well as its response to whistleblowers and investigators who expressed concern about reckless conduct," said Issa spokesman Frederick R. Hill. "If the Justice Department cannot provide assurances that it will meet its legal obligations, the committee has no other option than moving to hold Attorney General Holder in contempt."

If the committee cited Holder for criminal contempt, it would open a complicated process that requires the House speaker to schedule a floor vote for the full House on the matter. It would then move to the U.S. Attorney for the District of Columbia, who is an employee of the Justice Department.

Staff Writer Paul Kane contributed to this report.