Attorney General Eric Holder has agreed to appear before the House Judiciary Committee on Dec. 8 to talk about Operation Fast and Furious.

Holder's appearance was requested by House Oversight and Government Reform Chairman Darrell Issa (R-Calif.), as questions emerged over the Attorney General's level of involvement in the botched gun sting.

But while Issa and other Republicans have been zeroing in on the Attorney General's office in their investigation of Fast and Furious, defenders of DOJ leadership say the operation originated -- without adequate supervision -- within the Phoenix field office of the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF).

In a letter to Chairman Issa, the committee's ranking Democrat, Rep. Elijah Cummings (M.D.) called for a public hearing with former ATF director Kenneth Melson to get a clearer understanding of the operation.

"With respect to our own Committee's investigation," Cummings wrote, "I do not believe it will be viewed as legitimate or credible -- and I do not believe the public record will be complete -- without public testimony from Kenneth Melson."

Cummings said that Melson, as well as the former Deputy Director of ATF, William Hoover, stated in interviews that "they had not been aware of the controversial tactics being used in Operation Fast and Furious, had not authorized those tactics, and had not informed anyone at the Department of Justice headquarters about them. They stated that Operation Fast and Furious originated within the Phoenix Field Division, and that ATF headquarters failed to properly supervise it."

"A hearing with Mr. Melson would help the Committee and the American people better understand what mistakes were made in Operation Fast and Furious, how these tactics originated, who did and did not authorize them, and what steps are being taken to ensure that they are not used again," wrote Cummings.

Melson's attorney has indicated that he would be "pleased to cooperate," according to Cummings' office.