WASHINGTON – Attorney General William Barr warned a House committee that he could refuse to appear at Thursday's hearing on the Justice Department's handling of the Russia investigation if lawmakers go through with a plan to let staff lawyers question him.

Barr's threat is an escalation in the tension between House leaders and the Trump administration, which vowed to resist Democratic efforts to probe more deeply into President Donald Trump's conduct in office and his outside business dealings.

Barr is scheduled to make two appearances before Congress this week to answer questions about the special counsel investigation. The first, on Wednesday, is before the Republican-controlled Senate Judiciary Committee.

House Judiciary Committee Chairman Jerry Nadler, D-N.Y., who leads an effort to seek a complete version of Russia special counsel Robert Mueller's inquiry, proposed that Barr be questioned Thursday by committee counsels in addition to lawmakers. Nadler said Barr should attend a separate, closed-door meeting with the panel.

Want news from USA TODAY on WhatsApp? Click this link on your mobile device to get started

Since Mueller's report was made public this month, Democrats have sought to question the attorney general about his decision to clear Trump of obstruction of justice after the special counsel's team highlighted numerous examples in which the president attempted to limit or derail Mueller's investigation.

Barr intervened when Mueller declined to express a view on whether Trump's conduct was criminal. On the central question of whether Trump or his presidential campaign conspired with the Russian government to tilt the 2016 election, the special counsel found insufficient evidence to support such a conclusion.

More:Trump repeatedly tried to impede the Russia inquiry, Mueller report says. Was it obstruction?

More:Attorney General William Barr faces a political firestorm after release of the Mueller report

Sunday, a senior Justice official said Barr initially agreed to appear before the House committee to be questioned by lawmakers only.

While officials discussed the format for Thursday's session, the official said that if committee leaders demanded that Barr be questioned by the panel’s counsels or staffers, the attorney general would not attend.

The dispute was first reported by CNN.

In a statement Sunday, House Judiciary Republicans called the Democrats' demands "abusive" and without precedent.

"Attorney General Barr wasn’t asked to testify before the committee – he offered," the GOP members said. "What actual precedent is there for our committee making such demands of a sitting attorney general as part of our oversight duties? The attorney general isn’t a fact witness.”

Beyond the Judiciary Committee, House Democrats seek a trove of information from Trump administration officials as part of wide-ranging inquiries into Trump's conduct before and after he became president. Trump asserted last week that the administration would challenge "all the subpoenas."