The letter will likely buoy congressional Democrats’ accusations that Barr mischaracterized Mueller’s report on purpose in order to protect the president. Its disclosure comes on the eve of Barr’s public testimony before the Senate Judiciary Committee, and amid a back-and-forth between the Justice Department and the House Judiciary Committee over whether committee staff can question Barr separately on Thursday.

The letter also reveals a widening gulf between Barr and Mueller, who have been friends for decades, and is a sign that the special counsel’s team was angry with how Barr characterized the findings.

A Justice Department spokeswoman, Kerri Kupec, said in a statement that Barr called Mueller after receiving the letter to discuss it further.

“The Special Counsel emphasized that nothing in the Attorney General’s March 24 letter was inaccurate or misleading,” Kupec said. “But, he expressed frustration over the lack of context and the resulting media coverage regarding the Special Counsel’s obstruction analysis. They then discussed whether additional context from the report would be helpful and could be quickly released. However, the Attorney General ultimately determined that it would not be productive to release the report in piecemeal fashion.”

“The Attorney General and the Special Counsel agreed to get the full report out with necessary redactions as expeditiously as possible,” Kupec’s statement continued. “The next day, the Attorney General sent a letter to Congress reiterating that his March 24 letter was not intended to be a summary of the report, but instead only stated the Special Counsel’s principal conclusions, and volunteered to testify before both Senate and House Judiciary Committees on May 1st and 2nd.”

A spokesman for the special counsel’s office, Peter Carr, declined to comment. The letter was first reported by The Washington Post.

House Speaker Nancy Pelosi admonished Barr on Tuesday night and demanded that he release an unredacted version of Mueller’s report.

“Attorney General Barr misled the public and owes the American people answers,” she wrote on Twitter. “It’s time for DOJ to release the full report & all underlying docs — and finally allow Mueller to testify. Americans deserve the facts. Barr must stop standing in the way.“

Senate Minority Leader Chuck Schumer (D-N.Y.) said Barr needed to bring the special counsel’s March 27 letter with him on Wednesday.

“In light of Mueller’s letter, the misleading nature of Barr’s 4/10 testimony & 4/18 press conference is even more glaring,” Schumer tweeted. “Barr must bring the letter with him when he testifies in the Senate tomorrow. And it’s time for Mueller to testify publicly. Now.“

Barr is expected to tell lawmakers on Wednesday that he released his initial letter because “I determined that it was in the public interest for the department to announce the investigation’s bottom-line conclusions — that is, the determination whether a provable crime has been committed or not,” according to a prepared opening statement released late Tuesday.

Rep. Jerry Nadler (D-N.Y.), chairman of the House Judiciary Committee, released a statement expressing outrage over the reports and demanded a copy of the letter by 10 a.m. Wednesday.

“The Attorney General has expressed some reluctance to appear before the House Judiciary Committee this Thursday,” Nadler said. “These reports make it that much more important for him to appear and answer our questions. The Department of Justice has also been reluctant to confirm a date for Special Counsel Mueller to testify. Given this evening’s reports, I will press the Department to schedule that hearing without delay.”

Nadler has been working to secure testimony from Mueller but there has been little back-and-forth with Justice Department officials to get it on the schedule.

Barr said at a news conference earlier this month that he had “no objection” to Mueller‘s appearing before Congress to discuss his report. Carr declined comment when asked about the status of talks to have Mueller testify to House Judiciary by May 23.

A spokesperson for Republicans on the House Judiciary Committee issued a statement defending the attorney general.

“Attorney General Barr released the special counsel’s report voluntarily, and with minimal redactions, to answer any questions about the context and substance of the special counsel’s investigation,” the statement said. “Recent media reports give us more reason than ever to have confidence in the attorney general by providing insight into how the attorney general and the special counsel successfully collaborated to navigate a very difficult and historically momentous situation, culminating in the release of the Mueller report, which provides the account of the special counsel’s investigation in the words of Mr. Mueller and his team. As the Senate Judiciary Committee prepares for tomorrow’s hearing, House Democrats have another opportunity to put partisan politics aside and recognize Attorney General Barr has conducted himself in an exemplary manner.”

In his congressional testimony earlier this month, Barr made no mention of Mueller‘s complaining to him in a letter or in a phone call about the March 24 letter or the response to it.

“Reports have emerged recently, General, that members of the Special Counsel’s team are frustrated at some level with the limited information included in your March 24 letter,” Rep. Charlie Crist (D-Fla.) said at the April 10 hearing. “That it does not adequately or accurately, necessarily, portray the report’s findings. Do you know what they’re referencing with that?”

“No, I don’t,” Barr replied. “I think — I think — I suspect that they probably wanted, you know, more put out. But in my view, I was not interested in putting out summaries. … I think any summary regardless of who prepares it not only runs the risk of being underinclusive or overinclusive but also would trigger a lot of discussion and analysis that really should await everything coming out at once.”

A senior Justice Department official said on Tuesday that Barr was mystified by the letter Mueller and his team had sent objecting to Barr’s March 24 letter.

“The attorney general and his senior staff — they were very surprised at the complaint and at the frustration,” said the official, who spoke on the condition of anonymity. “They were actually shocked that there was a problem.”

Asked about lawmakers’ complaints that Barr’s statement to Crist was evasive, the senior official said that although the attorney general did not mention the letter directly, he was conveying the thrust of Mueller’s complaint about Barr’s letter.

“That is why he referenced the summary and said he was not interested in putting them out. … He was alluding to the letter,” the official said.

The official told POLITICO the phone call between Barr and Mueller on the issue was cordial, despite the attorney general’s difficulty fathoming the complaint. “They’ve been colleagues a long time and they dealt with it and that’s it,” the official said.

However, Mueller’s objection did contribute to Barr’s decision to send another letter to Congress on March 29 updating lawmakers on the review of the report and emphasizing that the March 24 letter was not intended as a “summary” of the report.

The official said Barr didn’t disclose Mueller’s letter or the conversation about it over the past month because he considered it internal communications between department officials. “Mueller works for Barr,” the official added.

Chuck Rosenberg, the former acting director of the Drug Enforcement Administration. who served as Mueller’s counsel while he was FBI director in the early 2000‘s, said it was “very rare“ for Justice Department officials to put anything in writing, as Mueller did.

“We are conditioned not to ‘go to paper,‘” Rosenberg said. “And the idea behind that is that we‘re all part of the same department and we‘re not trying to corner each other. There are times you get mad, or frustrated, and think someone is making a bad decision. But you pick up the phone and call them. I think I only went to paper a handful of times in 20 years at the Justice Department. In the time I worked for Bob in the FBI, I can‘t think of a time he did that.“

James Schultz, a former associate counsel in the Trump White House, in an interview Tuesday came to Barr’s defense on the March 24 letter.

“He needed to say something or there’d be this constant drumbeat,” Schultz said. “He gave an accurate depiction of it, but the fact that special counsel Mueller felt there wasn’t enough context, that’s the risk you run by being responsive early on.”

Indeed, the criticism of Barr, including calls from some Democrats for his resignation, were met with incredulity in some legal circles.

“Barr step down? Are you fucking insane?” said Sol Wisenberg, a former deputy on Kenneth Starr’s independent counsel investigation into President Bill Clinton.

Others went so far as to suggest Barr himself faces legal jeopardy.

“When our esteemed Attorney General of the United States testifies before the Senate Judiciary Committee tomorrow, if I were questioning him, I would start off by saying: ‘Sir, you have the right to remain silent. Anything you say can and will be used against you. . . .,’” Gene Rossi, a former federal prosecutor from Virginia, said in an email to POLITICO.

Either way, some say Mueller’s letter has done significant damage to Barr’s credibility.

“We obviously need to see the letter, but I know it exists,” Greg Brower, the former head of the FBI congressional affairs office, said in an email. “I have been saying from the beginning that the worst thing Barr could do is mischaracterize the report. Well, now we have Mueller himself saying Barr did just that. NOT good.”

Julian Epstein, a former senior House Judiciary Committee Democratic aide who worked on the Clinton impeachment fight, said in an email: “The Mueller complaint that Barr skillfully spun his report to the news media will not change the overall arc of where Congress is headed, but underscores the cartoonish efforts to do damage control by playing press secretary rather than attorney general,”

“In so doing, Barr is completely misserving Trump’s interests by pouring more kerosene on a fire that has thus far consumed the Trump presidency.” Epstein added. “This was amateur hour by an AG we all thought was more a pro.”

Mueller’s chief complaint in the letter appeared to center on Barr’s characterization of the special counsel’s probe into potential obstruction of justice by President Donald Trump, and Barr’s refusal to release the executive summaries included in Mueller’s report. Barr quoted from portions of Mueller’s report in the four-page memo, and noted that the special counsel did not make a decision one way or another on whether the president had obstructed justice.

Barr and Deputy Attorney General Rod Rosenstein, however, came to their own conclusion, finding that “the evidence developed during the Special Counsel’s investigation is not sufficient to establish that the President committed an obstruction-of-justice offense.”

Barr also held a news conference two hours before the final report was released to the public, announcing that Mueller had found “no collusion” between the Trump campaign and Russia, despite Mueller’s assertion in the report that he not examine the evidence through the lens of “collusion” since that is not a legal term.

Mueller and his team notably stayed away from Barr’s news conference when he rolled out the release of the special counsel’s findings flanked by Rosenstein and Ed O’Callaghan, the acting principal associate deputy attorney general, who had the most frequent supervisor interactions with the Russia investigators.

Rosenstein submitted his resignation on Monday and is set to leave the Justice Department on May 11. He joked about the Barr news conference in a speech last week.

“Last week, the big topic of discussion was, ‘What were you thinking when you stood behind Bill Barr at that press conference, with a deadpan expression?’” Rosenstein said. “The answer is I was thinking, ‘My job is to stand here with a deadpan expression.’”

“Can you imagine if I did anything other than stand there at the press conference?” he added. “Imagine the reaction and the commentary if I had smiled or grimaced.”

Trump’s personal attorney Rudy Giuliani said via text that he was “not aware” of Mueller’s letter to Barr. “If Mueller couldn’t make a decision on obstruction, there was no case,” Giuliani replied later Tuesday when asked for comment on the newly-disclosed dispute between the special counsel and attorney general. “He said he could not conclude that the President obstructed Justice. Case over. Who cares if he can’t exonerate him. He was appointed to make decisions not to punt. If he was unable to that tells everyone all they need to know. For a prosecutor, indecision is a decision.”

Four sourcestold POLITICO in early April that Mueller’s team was concerned with how the attorney general handled the rollout of the special counsel’s findings.

“Yeah, there was frustration with the summary and that there’s a hope that people have access to the actual underlying report,” a source familiar with conversations about the Barr letter said then. “I think it’s fair to say there was generalized frustration.”

One of those sources close to some of the Mueller prosecutors said in an interview after the report’s release last week that at least in the way of the redactions, the special counsel’s team was satisfied.

“Ninety percent is in there, especially on the obstruction stuff,” the source said.

Andrew Desiderio contributed to this report.