Attorney General William Barr (Joshua Roberts/Reuters)

Attorney General William Barr has threatened defiance of the House Judiciary Committee over the Mueller Report, refusing to testify about findings over Trump-Russia links and Donald Trump’s obstruction of justice.

Barr is objecting to the format of Thursday’s hearing. After 5-minute rounds of questioning from legislators, staff lawyers will have 30 minutes to follow up on issues.

Justice Department spokeswoman Kerri Kupec said Sunday, “The Attorney General agreed to appear before Congress. Therefore, members of Congress should be the ones doing the questioning.”

Committee chairman Rep. Jerrold Nadler said Barr will be subpoenaed if he refuses to appear:

The witness is not going to tell the committee how to conduct its hearing, period….We will have to subpoena him, and we will have to use whatever means we can to enforce the subpoena.

Since taking office in February, Barr has protected Trump from the investigation. Two days after receiving the Mueller Report in late March, he set aside the staff summaries and issued a four-page letter trying to clear Trump of any political responsibility, as well as criminal liability.

Just before the public release of the Report earlier this month, Barr gave a pre-emptory press conference, issuing the misleading claim that Mueller had found “no collusion” and quashing the possibility that Trump obstructed justice.

But that position has been shaken as the Report has been examined by journalists and analysts. Mueller sets out “numerous contacts” between the Trump campaign and transition, Russian officials, and intermediaries such as WikiLeaks — including over the publication of material, stolen by Russian military intelligence, to damage Democratic nominee Hillary Clinton. In eight of 10 cases, it finds that Trump obstructed or attempted to obstruct justice.

Democrats, who control the House, have promised “major hearings” into both Trump-Russia and Trump’s financial affairs and possible conflicts of interest.

In response, the White House is aggressively trying to block any significant testimony. It has instructed potential witnesses — such as former White House Counsel Donald McGahn, a central figure in Trump’s attempted obstruction, including the effort to fire Mueller — not to comply with subpoenas.

The White House has also blocked a former official from answering questions about granting security clearances — including a top-secret clearance to Trump’s son-in-law Jared Kushner. US agencies refused to issue the clearance because of Kushner’s failure to disclose financial matters and meetings with foreign official before becoming a White House advisor.

Last week the Treasury again refused to comply with a House Committee request for Trump’s tax returns and financial statements.

Rep. Jamie Raskin, a Democrat member of the Judiciary Committee, reacted to Barr’s threat:

The President is trying to pull the plug on congressional oversight power, and this is yet another assault on the legislative function when the witness suggests he will dictate a format of questioning. The members are unhappy with the executive branch trying to dictate our work.