"This is absurd", Sanders said.
However, what has not been made public is that law enforcement officials also sought to determine whether the president's own actions constituted a possible threat to national security, according to the Times. They also wanted to determine whether the president "was knowingly working for Russian Federation or had unwittingly fallen under Moscow's influence".
"In fact, when I chose to just do it, I said to myself, I said: 'You know, this Russian Federation thing with Trump and Russian Federation is a made up story, it's an excuse by the Democrats for having lost an election that they should've won", the president told Holt at the time.
The FBI investigation was soon folded into Robert Mueller's inquiry into Russian interference in the 2016 vote and possible collusion between his campaign and Moscow, it said, adding that it was unclear if the counterintelligence aspect was still being pursued.
Mr Trump's behaviour in the days around Mr Comey's May 2017 firing, specifically two instances in which he seemed to tie Mr Comey's ousting to the Russian Federation investigation, helped trigger the counterintelligence part of the investigation, according to the Times' sources.
President Trump said he was unaware of Mr. Whitaker's past statements about Mr. Mueller's probe and that he would "not get involved" if Mr. Whitaker moved to curtail it.
Comey has since condemned Trump as "morally unfit" to hold the office of president, and said there was "certainly some evidence of obstruction of justice".
But while the president has slammed the probe as baseless, it has issued dozens of indictments and steadily chalked up convictions of some of the president's close associates - including his former personal lawyer, his ex-campaign chief and his former national security advisor.
In this image released by ABC News, former Federal Bureau of Investigation director James Comey appears at an interview with George Stephanopoulos set to air during a prime time "20/20" special on April 15, 2018 on the ABC Television Network.
The Times also reported that "some former law enforcement officials outside the investigation have questioned whether agents overstepped" in opening an investigation into that angle.
Friday's remarkable report is sure to ramp up the pressure for a White House already feeling the heat from months of investigations.
Trump's former campaign chairman Paul Manafort in August 2018 was convicted of financial crisis and later pleaded guilty to conspiring to defraud the U.S. and conspiring to obstruct justice.