[Read Mr. Barr’s letter.]

Mr. Barr, who was sworn in as attorney general last month, has committed since his confirmation hearing to making public as much of the highly anticipated report as possible. But his declaration on Sunday, two days after the report was delivered to him, that Mr. Trump had not illegally obstructed justice drew swift condemnation from Democrats. They accused him of stepping in where Mr. Mueller had declined to make a prosecutorial decision.

Mr. Barr said that Rod J. Rosenstein, the deputy attorney general, concurred with his finding on the obstruction question but noted that Mr. Mueller, while he declined to make a judgment on the issue, also stopped short of explicitly exonerating the president.

The House passed a resolution this month, 420 to 0, demanding that the full report be released. Democrats have called for the Justice Department to send them the underlying investigative files as well.

“Congress requires the full and complete Mueller report, without redactions, as well as access to the underlying evidence,” Jerrold Nadler, Democrat of New York and chairman of the House Judiciary Committee, said in a statement in response to Mr. Barr’s letter.

Mr. Trump has already seized on Mr. Barr’s findings as vindication, declaring during a rally with supporters on Thursday night in Grand Rapids, Mich., that the cloud hanging over his presidency had finally cleared.