(CNN) President Donald Trump has ordered all major US intelligence agencies to assist Attorney General William Barr in his review of surveillance issues surrounding Trump's 2016 presidential campaign, delegating significant authority to Barr to declassify sensitive intelligence materials as the attorney general sees fit.

The formal memorandum released by the White House late Thursday evening directs the heads of each agency to "promptly provide" information as Barr requests.

The move represents a new step in expanding Barr's powers as he embarks on a controversial review of the early counterintelligence work that kicked off the Russia investigation, which has loomed large over Trump's first term in office. But the move could also serve as a prelude to a larger declassification effort Trump has floated since last fall as he's battled his own intelligence agencies and accused former officials, without evidence, of conspiring against him.

"Today's action will help ensure that all Americans learn the truth about the events that occurred, and the actions that were taken, during the last Presidential election and will restore confidence in our public institutions," White House press secretary Sarah Sanders said in a statement.

Trump on Friday insisted Barr's review is being done in the name of transparency and said his decision to grant Barr substantial power is not about political payback, even as the President continued to call the investigation into him and his campaign an "attempted take down."

"It's not payback, I don't care about payback," Trump said. "This is about finding out what happened ... We're exposing everything."

Trump defended his decision to grant Barr declassification authority, praising him as a "highly-respected man."

READ: Trump orders intel agencies to assist Barr with review of Russia probe

In a statement Friday, the director of national intelligence, Dan Coats, said he is confident Barr will "protect highly-sensitive classified information that, if publicly released, would put our national security at risk." The statement refers to "Russian interference" efforts in the 2016 election but does not mention alleged wrongdoing by US authorities.

While Trump had previously lamented the lack of investigation into the origins of how those associated with his presidential campaign came under investigation, Barr has taken up the President's call to action.

As CNN has previously reported, Barr is working closely with the heads of the CIA, the FBI and the Office of the Director of National Intelligence to review surveillance activities surrounding the 2016 presidential campaign. Barr is leading the review with US Attorney John Durham, a career federal prosecutor in Connecticut.

The Justice Department's internal watchdog is separately investigating how the FBI obtained surveillance orders to monitor former Trump campaign aide Carter Page. Thursday's move by Trump to delegate declassification authority to Barr may set the stage for him to make certain documents related to Inspector General Michael Horowitz's work publicly available that would otherwise stay under wraps.

Barr has not provided any details on Horowitz's conclusions, but he suggested during a congressional hearing last month that "spying did occur" -- touching off a firestorm over his language and criticism for generally declining to further elaborate on such incendiary claims.

"We should be worried about whether government officials abused their power and put their thumb on the scale," Barr told Fox News last week, adding that his questions haven't been adequately answered thus far. "And so I'm not saying that happened, but I'm saying that we have to look at that."

US officials say that while many interpreted Barr's initial spying comments to be directed at the FBI, in reality, the core of his concern is the activities of other intelligence agencies at the start of the Russia probe.

This story has been updated.