When Mr. Barr was briefed on the investigation this month, he was told that there would be no more subpoenas or indictments, and that Mr. Mueller’s team was ready to wrap up in mid-March, according to people familiar with the investigation who were not authorized to discuss it. The special counsel’s office later notified Mr. Barr that it needed a few additional days to take care of administrative issues, which pushed the delivery to Friday.

Without certainty about what Mr. Barr would disclose or when, House Democrats convened a 30-minute conference call on Saturday afternoon to line up talking points. Democrats led by Speaker Nancy Pelosi of California have begun insisting that only the release of Mr. Mueller’s full report and underlying findings will be sufficient so that Democrat-led House committees can conduct their own scrutiny of Mr. Trump.

The top Democrats on nearly a dozen House and Senate committees sent letters on Friday to the F.B.I., the Justice Department, the White House and other federal agencies demanding that all documents, communication and evidence amassed by Mr. Mueller and his team be preserved because Congress might request access to it.

“Congress requires the full report and the underlying documents so that the committees can proceed with their independent work, including oversight and legislating to address any issues the Mueller report may raise,” Ms. Pelosi wrote in a letter to fellow Democrats before the call.

During the call, she added that she would reject any offer from the Justice Department to brief the bipartisan Gang of Eight House and Senate leaders or some other configuration of lawmakers in a classified setting on findings that are not made public, according to a person present. Ms. Pelosi said she would insist any briefing be unclassified to allow lawmakers to discuss the full investigative findings publicly.

Republican leaders convened their own brief call on Friday night, after the Justice Department notified Congress that it had received the report from Mr. Mueller’s office, but it was primarily limited to logistics, according to one person with knowledge of the call. Welcoming the news that the special counsel would seek no further indictments, members of the president’s party were cautiously optimistic.

The Republican National Committee circulated talking points to allies on Friday that emphasized Mr. Trump’s cooperation with the inquiry and appeared to set the stage for the president and his party to claim political victory. They asserted that “speculation” about interference with the investigation had been proved “dead wrong.”