President Donald Trump is defending his unprecedented the decision to give his Justice Department chief unfettered access to the country's deepest foreign intelligence secrets amid an outcry from the spy community and a veiled warning from the US intelligence czar.

The president said Attorney General Bill Barr needed unilateral power to declassify any top secret material to get to the roots of the 2016-2018 investigation into whether his election campaign colluded with Russia. Barr "will be able to see how this hoax, how the hoax or witch hunt started, and why it started," Trump said.

"It was an attempted coup or an attempted takedown of the president of the United States. It should never ever happen to anybody else, so it's very important."

But politicians and former intelligence community leaders said Trump and Barr are threatening to expose the country's most protected sources of secrets on Russia to mount a political attack on a legitimate investigation that exposed a serious threat to the United States.

Critics said Trump and Barr, who has become one of the president's staunchest defenders were playing fast and loose with intelligence for political reasons.

Former CIA deputy director John McLaughlin called for Congress to thwart the move. "Giving Barr declassification authority for this investigation is a really bad idea," he said on Twitter.

The subsequent investigation, which included authorized national security wiretaps found a concerted effort by Russia to develop contacts, exchange information and negotiate deals, from a Trump real estate project in Moscow to the lifting of sanctions on Russia.

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