Some members of special counsel Robert Mueller's team have expressed frustration that Attorney General William Barr cleared President Donald Trump of obstruction of justice, and they believe the evidence that Trump sought to impede the investigation is stronger than Barr suggested in his March letter summarizing Mueller's findings, a U.S. official who has spoken with the members tells NBC News.

Justice Department officials say Barr had no choice but to render a judgment, because the special counsel regulations say that he is ultimately in charge of the investigation. If Mueller believed Trump was guilty of obstruction, he could have said so, the officials argue — but he didn't do that in his report.

Three government officials have told NBC News that a dispute within the special counsel's office on the facts and the law was one factor behind Mueller's decision not to make a call on the obstruction question.

The lawyers and FBI agents on Mueller's team could not reach an agreement about whether Trump's conduct amounted to a corrupt — and therefore illegal — effort to impede the probe, the three officials said. As a result, Barr, after consulting with Deputy Attorney General Rod Rosenstein, stepped in to clear the president, saying the evidence did not amount to a prosecutable case of obstruction of justice.

The feelings of some members of Mueller's team do not change the attorney general's legal conclusions — which cleared Trump on both obstruction and conspiracy with Russia. But the political impact could be huge, as Democrats seek more information on Mueller's findings.

The New York Times and The Washington Post first reported that some members of the Mueller team were upset with how Barr portrayed the evidence.

A former federal prosecutor familiar with Barr's thinking said the attorney general believed the obstruction case was complicated by the fact that the questionable actions taken by Trump, such as firing his FBI director, were authorized under the powers of the presidency.

At least one faction within the office says their intent was to leave the legal question open for Congress and the public to examine the evidence, the U.S. official who has spoken to them said. It's not clear how Mueller himself feels about the matter.

On Thursday morning, the Justice Department issued a statement saying that Barr had decided to release the "bottom-line findings" and conclusions of the Mueller report immediately, without attempting to summarize it. The statement said he did so with the understanding that the report would be made public once confidential information in it had been redacted.

"The Department continues to work with the Special Counsel on appropriate redactions to the report so that it can be released to Congress and the public," said the statement issued by the department spokesperson, Kerri Kupec.

House Judiciary Committee Chairman Jerry Nadler, D-N.Y., sent a letter to Barr later in the day urging him to release to the public any "summaries" in the report prepared by the special counsel's office. Nadler also requested that Barr hand over to the committee "all communications between the special counsel's office and the [Justice] Department regarding the report."

"You have already provided an interpretation of the special counsel's conclusions in a fashion that appears to minimize the implications of the report as to the president," Nadler said in the letter. "Releasing the summaries—without delay—would begin to allow the American people to judge the facts for themselves."

Mueller told Barr and his deputy Rod Rosenstein four weeks ago that he would not be making a decision about obstruction — news that came as a surprise to them, Justice Department officials said. Barr's letter said Rosenstein agreed with his decision that there was no case that the president had obstructed justice.

READ: Barr's letter to Congress

It's also unclear whether Barr coordinated his March 24 letter in advance with Mueller. Many longtime observers of Mueller are puzzled as to why he didn't render his own judgment on a core matter in his investigation.

The DOJ policy that says a sitting president can't be charged with a crime wasn't a factor in the dispute within Mueller's team, according to one senior U.S. official in a position to know. Rather, lawyers disagreed about whether they could prove that Trump had criminal intent as he took a variety of actions that seemed designed to shut down the investigation, from firing FBI Director James Comey, to ordering the dismissal of Mueller, only to back off when his White House counsel threatened to quit, according to The New York Times and not confirmed by NBC News.

The official who has spoken to members of Mueller's team says they described the evidence on obstruction as compelling and said it includes more information than has been made public.

According to a senior law enforcement official who has spoken to members of Mueller's team, Mueller team members say it includes detailed accounts of Trump campaign contacts with Russia. While Mueller found no coordination or criminal conspiracy, the official said, some on the special counsel's team say his findings paint a picture of a campaign whose members were manipulated by a sophisticated Russian intelligence operation. Some of that information may be classified, the official said, so it's not clear whether it will be released in a few weeks when Barr makes public a redacted version of the Mueller report.

Trump lawyers have pushed back against some of this reporting.

"They're a bunch of sneaky, unethical leakers," Rudy Giuliani said on Fox News about the Mueller team. "And they are rabid Democrats who hate the president of the United States, and I can't tell you how much false information they leaked during the course of the investigation."