But Mueller himself took no stance on the weight of the evidence of obstruction, Barr noted, raising doubts over whether Trump had truly been exonerated by the report.
Barr has been under pressure since his March 24 summary to release the entire report, which wrapped up a 22-month investigation that saw 34 people charged, including six former Trump aides.
But he has stressed he will only release a version with intelligence information and secret material from the investigation grand jury convened by Mueller blacked out.
Critics say the grand jury material is crucial to understanding whether there was evidence of criminal behavior by Trump, and Democrats in Congress are demanding an unexpurgated version of the report.
Since Barr's initial summary Trump and the White House have been pushing the view that the probe was unwarranted from the beginning, comprised biased investigators and involved allegedly illegal spying on his campaign by the FBI.
"The Mueller Report, which was written by 18 Angry Democrats who also happen to be Trump Haters (and Clinton Supporters), should have focused on the people who SPIED on my 2016 Campaign, and others who fabricated the whole Russia Hoax," Trump tweeted Monday.
"Since there was no Collusion, why was there an Investigation in the first place! Answer - Dirty Cops, Dems and Crooked Hillary!" he wrote.