WASHINGTON — Six Democratic committee chairs in the House sent a letter to Attorney General William Barr on Monday requesting that he submit the full report from special counsel Robert Mueller's Russia investigation to Congress by April 2.

In a three-page letter to Barr, the lawmakers wrote that his summary of the Mueller report "is not sufficient for Congress."

"We look forward to receiving the report in full no later than April 2, and to begin receiving the underlying evidence and documents that same day," the letter said.

The top House Democrats argued that providing the report "in complete and unredacted form," along with the underlying evidence and materials, would be fully consistent with the Department of Justice's practice and precedent with Congress.

"To the extent that you believe applicable law limits your ability to comply, we urge you to begin the process of consultation with us immediately in order to establish shared parameters for resolving those issues without delay," they wrote.

The letter was signed by House Judiciary Committee Chairman Jerry Nadler, D-N.Y., House Oversight Committee Chairman Elijah Cummings, D-Md., House Intelligence Committee Chairman Adam Schiff, D-Calif., House Financial Services Committee Chairwoman Maxine Waters, D-Calif., Ways and Means Committee Chairman Richard Neal, D-Mass., and House Foreign Affairs Chairman Eliot Engel, D-N.Y.

"All I’m interested in is for them to release the full report, the full Mueller report," Speaker Nancy Pelosi, D-Calif., told reporters Monday night at the Capitol.

Their request comes a day after Barr submitted to Congress and made public his four-page summary of Mueller's report, which said the special counsel did not find proof of collusion between the Trump campaign and Russia during the 2016 election and provided no opinion on whether the president had obstructed justice, instead leaving that to Barr, who said there was not sufficient evidence to move forward.

In his letter, Barr said the Mueller report states that the investigation "did not establish that members of the Trump Campaign conspired or coordinated" with Russia. Barr also wrote that he and Deputy Attorney General Rod Rosenstein "have concluded that the evidence developed during the special counsel's investigation is not sufficient to establish that the President committed an obstruction-of-justice offense."

Still, Barr continued by noting Mueller found that "while this report does not conclude that the President committed a crime, it does not exonerate him."

Democrats have demanded that the entire Mueller report and the corresponding documents and materials used during the investigation be made public. Barr has not committed to doing that in previous comments and testimony to Congress.

Meanwhile, Senate Majority Leader Mitch McConnell, R-Ky., on Monday blocked an effort by Senate Minority Leader Chuck Schumer to unanimously pass a non-binding measure stating that Congress wants Mueller’s report be made available to lawmakers and the public. The measure was passed in a unanimous House vote earlier this month.