President Donald Trump on Wednesday invoked executive privilege over the entirety of the special counsel Robert Mueller's final report on the Russia investigation and its underlying evidence.

Trump also asserted privilege over any other materials related to the Russia investigation that have been subpoenaed by Congress so far.

Earlier Wednesday, the House Judiciary Committee kicked off a vote on holding Attorney General William Barr in contempt of Congress.

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President Donald Trump on Wednesday asserted executive privilege over the entirety of the special counsel Robert Mueller's final report on the Russia investigation and its underlying evidence.

The president also invoked privilege over any other materials related to the Russia investigation that have been subpoenaed by Congress so far.

"This protective assertion of executive privilege ensures the President's ability to make a final decision whether to assert privilege following a full review of these materials," Assistant Attorney General Stephen E. Boyd said in a letter to the House Judiciary Committee.

The panel kicked off a hearing earlier Wednesday on holding Attorney General William Barr in contempt of Congress for refusing to turn over an unredacted version of Mueller's report, its underlying evidence, and any grand-jury material in the document.

Read more: The White House is blocking Don McGahn from cooperating with Congress about the Mueller probe

The Justice Department said late Tuesday that it would advise Trump to invoke executive privilege if the committee and its chairman, Rep. Jerrold Nadler, moved forward to hold Barr in contempt.

"The American people see through Chairman Nadler's desperate ploy to distract from the President's historically successful agenda and our booming economy," the White House press secretary, Sarah Huckabee Sanders, said in a statement Wednesday. "Neither the White House nor Attorney General Barr will comply with Chairman Nadler's unlawful and reckless demands."

The statement continued: "Faced with Chairman Nadler's blatant abuse of power, and at the Attorney General's request, the President has no other option than to make a protective assertion of executive privilege."

Read more: Over 370 former federal prosecutors say they would have charged Trump with obstruction if he wasn't president

Trump's privilege assertion marks the latest escalation in the protracted tug-of-war between Congress and the Justice Department over Mueller's findings.

After Mueller turned in his final report on the Russia investigation to Barr in March, the attorney general released a summary of his "principal conclusions" of Mueller's findings to Congress and the public, saying Mueller did not find sufficient evidence to bring a conspiracy charge against Trump or anyone on his campaign.

Barr also said Mueller declined to make a "traditional prosecutorial judgment" on whether Trump obstructed justice. The attorney general went on to say that prosecutors laid out evidence on "both sides" of the issue and did not come to a conclusion because of "'difficult issues' of law and fact concerning whether the President's actions and intent could be viewed as obstruction."

Read more: Democratic senator accuses Attorney General Barr of lying to Congress in fiery exchange over Mueller's report

But last month, when the Justice Department finally released a redacted version of the report — which featured a roadmap of evidence against Trump and 11 potential instances of obstruction of justice — Barr drew immediate backlash for what Democrats described as an effort to shield the president by watering down Mueller's findings ahead of their release.

Last week, Barr was set to appear before the House and Senate judiciary committees for back-to-back days of testimony about the report and his decisions leading up to its release. Hours ahead of his appearance before the Senate panel, it surfaced that Mueller had written two letters to Barr expressing concerns about the way his findings had been portrayed by the attorney general.

After Barr was grilled by Senate Democrats about the letters and his oversight of the Russia investigation, the Justice Department said he would not appear before the House Judiciary Committee, led by Democrats, the next day.

The committee launched formal proceedings to hold him in contempt after he missed Monday's deadline to turn over the unredacted report and its underlying evidence.