[Read the contempt resolution here.]

At the same time, the Judiciary Committee was preparing to raise the pressure on Donald F. McGahn II, a former White House counsel and chief witness in the special counsel investigation, if he misses a Tuesday deadline to hand over key documents that the White House says are subject to executive privilege.

Mr. Barr, who refused to testify last week before the Judiciary Committee because of a dispute over format, has earned special ire, serving as a kind of surrogate punching bag for Democrats frustrated with Mr. Trump but leery of impeachment. If the full House follows suit and votes to hold Mr. Barr in contempt, it would be only the second time that the nation’s top law enforcement officer has been penalized by lawmakers in that way.

The Judiciary Committee’s chairman, Representative Jerrold Nadler of New York, said the Wednesday vote could still be avoided if the Justice Department changes course. Hours after Democrats announced their plan, a deputy to Mr. Barr wrote to hold out that possibility, kicking off a new round of exchanges with an uncertain outcome.

The deputy, Stephen E. Boyd, initially said that the department was willing to meet Wednesday afternoon — after the scheduled contempt vote — “to negotiate an accommodation that meets the legitimate interests of each of our coequal branches of government.” But the department later agreed to move the meeting up to Tuesday.

Democrats had compiled a 27-page contempt report documenting their interactions with the attorney general and the scope of their own investigation of obstruction of justice and abuse of power. Mr. Nadler said he hoped the two sides could resolve the dispute, but kept the contempt vote on Wednesday’s schedule.

“Even in redacted form, the special counsel’s report offers disturbing evidence and analysis that President Trump engaged in obstruction of justice at the highest levels,” Mr. Nadler said. “Congress must see the full report and underlying evidence to determine how to best move forward with oversight, legislation and other constitutional responsibilities.”

Among those “other responsibilities,” Mr. Nadler’s accompanying report said, was determining “whether to approve articles of impeachment with respect to the president or any other administration official, as well as the consideration of other steps such as censure or issuing criminal, civil or administrative referrals.”