(CNN) The House Judiciary Committee is moving forward with its plan for staff attorneys to question Attorney General William Barr at a Thursday hearing on special counsel Robert Mueller's investigation, even as the attorney general is threatening not to attend the hearing over the proposed format.

House Judiciary Chairman Jerry Nadler, a New York Democrat, scheduled a Wednesday committee vote to allow an additional hour of questioning at Thursday's hearing. The vote would allow members or staff to question Barr during the extra hour, which would be divided between Democrats and Republicans.

Barr has objected to the format that would have staff asking questions, raising the prospect he won't appear on Thursday. But Nadler told reporters Monday the issue wasn't up for negotiation.

"There is no middle ground," Nadler said. "It's none of the business of a witness to try to dictate try to a congressional committee what our procedures for questioning him are."

Nadler added that the Justice Department seemed to be "very afraid" to have Barr answer questions from committee staff.

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