Barr suggested that he would focus on former senior leaders at the FBI and Justice Department.

"To the extent there was overreach, what we have to be concerned about is a few people at the top getting it into their heads that they know better than the American people," said Barr. 

Barr will also review whether the infamous Steele dossier - a collection of salacious and unverified claims against Donald Trump, assembled by a former British spy and paid for by the Clinton campaign - was fabricated by the Russian government to trick the FBI and other US agencies. (Will Barr investigate whether Steele made the whole thing up for his client, Fusion GPS?)

"We now know that he was being falsely accused," Barr said of Trump. "We have to stop using the criminal justice process as a political weapon."

Mueller's report didn't say there were false accusations against Trump. It said the evidence of cooperation between the campaign and Russia "was not sufficient to support criminal charges." Investigators were unable to get a complete picture of the activities of some relevant people, the special counsel found.

Although Barr's review has only begun, it's helping to fuel a narrative long embraced by Trump and some of his Republican supporters: that the Russia investigation was politically motivated and concocted from false allegations in order to spy on Trump's campaign and ultimately undermine his presidency. -Bloomberg