(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."

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