Attorney general preparing a set of conclusions from Mueller report but isn’t expected to finish that work Saturday

Attorney General William Barr spent Saturday reviewing special counsel Robert Mueller’s report on his investigation into President Donald Trump and Russian election interference, but does not plan to release the conclusions on Saturday, a senior Justice Department official said.

Barr and Deputy Attorney General Rod Rosenstein were at the Justice Department Saturday morning, where they were reviewing Mueller's report and working on a summary of conclusions to provide to lawmakers.

A Justice Department official said Rosenstein and Barr, along with their key advisers, were working closely together to read and analyze the report, and prepare the principal conclusions that would be submitted to Congress.

"They're working basically hand in hand," the official said.

The official said very few people know the report's contents.

The attorney general announced Friday that Mueller's work had come to an end, and Barr spent the afternoon and early evening in his fifth-floor office reading the special counsel's final report - which one Justice Department official described as a "comprehensive" document.

Barr told lawmakers in a letter that he "may be in a position to advise you of the Special Counsel's principal conclusions" as early as this weekend. A Justice Department spokeswoman said those conclusions would be made public. The spokeswoman declined to otherwise describe what was in the report.

The submission of Mueller's report ended his closely watched inquiry, a probe that has engulfed the Trump administration since its inception, leading to criminal charges against 34 people, including six former Trump associates and advisers.

A senior Justice Department official said the special counsel has not recommended any further indictments - a revelation that buoyed Trump's supporters, even as additional Trump-related investigations continue in other parts of the Justice Department.

Democrats and others reacted to the end of Mueller's probe by calling for the full report to be released. Though Mueller is not recommending additional criminal charges, his findings could prove politically damaging to the president.

House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Charles Schumer, D-N.Y., issued a joint statement saying that the report and "underlying documentation" must be provided to Congress.

Two advocacy groups quickly filed lawsuits seeking to make Mueller's full report public.

Trump's supporters, meanwhile, took news of the report's filing as an optimistic indication that he was on the cusp of being vindicated after nearly two years under Mueller's microscope.

"The fact that there are no more indictments is a big deal," said David Bossie, a top Trump ally. "This president has had his entire two-year presidency under a cloud of this fake, made-up Russian collusion story."

Trump flew to his Florida resort on Friday, accompanied by senior aides and White House lawyers.

Rudolph W. Giuliani, one of the president's lawyers, said he has been counseling patience.

"My message is: We've all waited this long, let's just await the reading of what's disclosed and then we can have proper final reactions. There's too much assuming going on, on the other side, and we shouldn't fall into that trap," said Giuliani. "The best news is that the release means the case is over. But you can't say more, or know more, until you read it. I'm confident, as I've been from the start, that the president did nothing wrong and that will sustain him. For everything he's done, there's a clear explanation he can make to the public."

The conclusions that Barr is expected to release could be brief and high-level - which surely would leave lawmakers and others unsatisfied. Earlier this month, the House voted nearly unanimously to urge the Justice Department to release Mueller's report in its entirety.

Barr and Rosenstein have noted publicly that Justice Department policies generally discourage prosecutors from making public any unflattering information about those they decide not to charge, or information that is classified or gathered by a grand jury. In his letter to lawmakers Friday, Barr said he would consult with Rosenstein and Mueller, who remains special counsel though his investigation is complete, "to determine what other information from the report can be released to Congress and the public consistent with the law, including the Special Counsel regulations, and the Department's long-standing practices and policies."

Those discussions will likely last significantly beyond the weekend. And no matter what Barr decides, lawmakers might upend his plans by subpoenaing documents and summoning witnesses to testify about the now-concluded Mueller probe.

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The Washington Post’s Robert Costa contributed to this report.