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Attorney General William Barr is testifying before the Senate Judiciary Committee today. Tomorrow, he's scheduled to answer questions before the House Judiciary Committee — but there's been some drama over that hearing.

Barr warned House Democrats he wouldn't show up to Thursday's hearing if they stuck to the format the chairman has proposed for the questioning, according to a committee source with knowledge of the matter.

House Judiciary Chairman Jerry Nadler told CNN that Barr would not "dictate the format of the Judiciary Committee."

Asked what he would do if Barr doesn't comply, Nadler said, "Then we will have to subpoena him, and we will have to use whatever means we can to enforce the subpoena."

The proposed format: According to the source, Nadler wants all panel members to have one round of questioning of five minutes each, and a subsequent round of questioning of 30 minutes for each side, allowing both parties' committee counsels to also engage in questioning.

Barr has rejected those proposals for additional rounds of questioning, according to the source. The Justice Department has informed Nadler's office that Barr doesn't think the committee counsels should be allowed to question him, the source said, prompting the attorney general to threaten to not show up at all.