US President Donald Trump has asserted executive privilege over Special Counsel Robert Mueller's report and its underlying investigative materials.
The move came just minutes before the house's judiciary committee was poised to vote to hold Attorney General William Barr in contempt for defying a congressional subpoena to hand over the full unredacted report.
The White House accused the Democrat chairman of the panel, Jerrold Nadler, of a "blatant abuse of power" and added the president "has no other option than to make a protective assertion of executive privilege".
Trump's move will probably lead to a "protracted legal war" over Mueller’s 448-page report, according to NBC.
Mueller’s document addresses both the alleged obstruction of justice by Trump as well as Russian interference in the 2016 US elections.
In a letter to Nadler on Tuesday evening, Assistant Attorney General Stephen Boyd called the persistent requests for materials "unreasonable".
In a further letter on Wednesday, Boyd wrote he was "disappointed" at the panel's decision to reject the Department of Justice's request to delay the vote and advised the chairman of the assertion of executive privilege.
"You have made this assertion necessary by your insistence upon scheduling a premature contempt vote," he concluded.
"This is, of course, not how executive privilege works,” Nadler said in a statement late Tuesday.
"The White House waived these privileges long ago, and the department seemed open to sharing these materials with us earlier today. The department’s legal arguments are without credibility, merit, or legal or factual basis."
He said the committee would go ahead with its consideration of the contempt citation as planned.