The Justice Department warned it will ask the president to invoke executive privilege over the entire Mueller report if the committee does not cancel a planned vote to hold Attorney General William Barr in contempt Wednesday morning, according to a letter from Assistant Attorney General Stephen Boyd to the House Judiciary Committee Tuesday evening.

It's a sharp escalation of the ongoing dispute between the committee and the Justice Department, which spent the day Tuesday negotiating over the House Judiciary Committee's subpoena for the entire Mueller report and underlying materials. In a statement, Judiciary Committee Chairman Jerrold Nadler, Democrat of New York, said the subpoena vote would go forward as planned, in spite of the department's threat.

The committee's subpoena deadline lapsed Monday, launching the latest round of negotiations. House Democrats previously rejected the Justice Department's initial offer, which was to allow congressional leadership and the top Democrats and Republicans on the House and Senate Intelligence and Judiciary Committees to view a less redacted version of the report at the Justice Department, along with a handful of staff.

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After the subpoena deadline passed and Nadler scheduled a contempt vote for Wednesday, Justice Department officials came to the Capitol for a meeting and offered to increase the number of aides who could view the report from one to two per member, to allow members to take their notes with them instead of leaving them at the Justice Department, and to discuss the redactions with other members who were allowed to view the report, according to a letter Boyd sent Nadler Tuesday evening.

The committee countered by seeking access to the less-redacted report for all members of the House and Senate Intelligence and Judiciary Committees, as well as three staffers per side. They also sought the Justice Department's cooperation in asking for a court order to allow Congress to view portions of the report that were redacted because they contain grand jury material, and to begin a discussion this week about gaining access to underlying materials.

Boyd's letter said that allowing more members to view the report would "force the Department to risk violating court orders and rules in multiple ongoing prosecutions, as well as risk the disclosure of information that could compromise ongoing investigations." He also argued that the committee's request for the Justice Department to join them in seeking a court order for redacted grand jury materials is a violation of current law.

"Such unreasonable demands, together with the Committee's precipitous threat to hold the Attorney General in contempt, are a transparent attempt to short-circuit the constitutionally mandated accommodation process and provoke an unnecessary conflict between our branches of government. They are also counterproductive," Boyd wrote.

"In the face of the Committee's threatened contempt vote," he continued, "the Attorney General will be compelled to request that the President invoke executive privilege with respect to the materials subject to the subpoena." He asked the committee to postpone the subpoena's return date and the contempt vote until the president can make a determination.

The letter itself is not an assertion of executive privilege, but Boyd said that if the contempt vote goes ahead as planned the attorney general will advise the president to protectively assert privilege over the entire report.

In a statement, Nadler called the department's legal arguments "without credibility, merit, or legal or factual basis." He said the White House had already waived executive privilege over the report and noted that the Justice Department was open to sharing the materials earlier in the day.

"This kind of obstruction is dangerous," Nadler said. "The Department's decision reflects President Trump's blanket defiance of Congress's constitutionally mandated duties. In the coming days, I expect that Congress will have no choice but to confront the behavior of this lawless Administration. The Committee will also take a hard look at the officials who are enabling this cover up."

Nadler said the contempt vote would go forward as planned but encouraged the Justice Department to "think better of this last-minute outburst and return to negotiations."

The top Republican on the committee, Georgia Rep. Doug Collins, accused Democrats of being uninterested in examining the facts they were being offered by the Justice Department.

"I can't imagine a more illogical hill for a legislator to die on," he said.