Washington — Attorney General William Barr sparred with congressional Democrats on Sunday over the conditions for his highly anticipated testimony on special counsel Robert Mueller's report before the House Judiciary Committee later this week.

Barr, who Democrats have accused of protecting the president, wants to be questioned only by lawmakers on the committee — not by their staff and lawyers.

"The attorney general agreed to appear before Congress. Therefore, members of Congress should be the ones doing the questioning," Kerri Kupec, a Justice Department spokeswoman, said in a statement Sunday. "He remains happy to engage with members on their questions regarding the Mueller report."

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But Democrats believe Barr, as the committee's witness, should not dictate the parameters of the hearing, scheduled for Thursday morning. A spokesperson for the Democratic-controlled panel also said the Justice Department can't prohibit members of Congress from asking about redacted sections of the Mueller report.

Rep. Jerry Nadler, the committee chair, scheduled a vote on Wednesday to approve an additional hour of questioning — by both lawmakers and their staff and counsel — during Barr's testimony. The New York Democrat said he expects the attorney general to show up on Thursday, but vowed to issue subpoenas if Barr refuses to testify.

"If the attorney general is afraid to subject (himself) to questions where you can follow up, that may indicate lack of confidence in his own position," Nadler told reporters Monday. "And more to the point, we have to get to the bottom of these issues. That's why we've called him in. It's not up to the attorney general to tell the committee how to conduct its business."

A Justice Department official told CBS News negotiations between Barr's office and the House Judiciary Committee are ongoing. The attorney general's appearance before the Republican-controlled Senate Judiciary Committee on Wednesday is still on, the official added.

While his investigative team did not find the Trump campaign coordinated the Russian government, Mueller described in his report multiple concerted efforts by the president to hinder a probe he believed would eventually lead to the end his presidency.

Breaking with party leadership, some Democrats have cited the actions Mueller analyzed in his probe into whether Mr. Trump obstructed justice — which he did not reach a conclusion on — to call for the president's impeachment.