(FILES) In this file photo taken on May 29, 2019 Special Counsel Robert Mueller speaks (AFP)
President Donald Trump attacked Robert Mueller on Monday, even as he insisted he would not watch the special counsel's potentially damaging Congressional testimony this week about the two-year Russia investigation.
Two days before Mueller testifies -- answering questions for the first time about his high-stakes probe into Russian election meddling and Trump's alleged obstruction -- the president repeated his longstanding claim it was a biased "witch hunt."
The US leader also repeated his false claim that Mueller's final report, released in April, found no collusion with Russia by the 2016 Trump campaign team and no obstruction of justice by the president himself.
"Highly conflicted Robert Mueller should not be given another bite at the apple. In the end it will be bad for him and the phony Democrats in Congress who have done nothing but waste time on this ridiculous Witch Hunt," Trump tweeted.
"Result of the Mueller Report, NO COLLUSION, NO OBSTRUCTION!"
Trump -- who is known to have closely followed previous testimony related to the Russia probe -- later told reporters he would not be watching Mueller's much-awaited, nationally broadcast appearance on Wednesday.
"We have no collusion, no obstruction, a total no collusion finding," Trump said again. "They are wasting their time."
Potentially damaging testimony
Whether Trump watches or not, White House officials and the president's lawyers will be closely monitoring what Mueller tells members of the Democratic-led House Judiciary and Intelligence Committees.
Mueller's 448-page report documents extensive contacts between the Trump campaign and Russians, including attempts to cooperate or collude, neither of which is a specific crime.
But Mueller ruled in the end that there was not enough evidence to recommend charges of criminal conspiracy, the main legal charge he could make use of.
The veteran prosecutor and former FBI director also laid out in detail 10 instances when Trump allegedly tried to obstruct the investigation.
But he said he was prevented from recommending charges against Trump because he was prohibited by Justice Department rules from lodging criminal charges against a sitting president.
That left it to Congress to determine whether Trump committed a crime, and a minority of Democrats are pressing for the House to impeach the president.
How Mueller describes the obstruction allegations could make his live testimony explosive, potentially impacting the pressure to impeach Trump, and the president's own campaign for reelection next year.
"We want the American people to hear directly from Special Counsel Mueller on what his investigation found," Representative Jerry Nadler, the chairman of the House Judiciary Committee said on Sunday.
"The report presents very substantial evidence that the president is guilty of high crimes and misdemeanors," he said, using the legal phrase that serves as the basis for impeachment.
Members of both parties were reportedly rehearsing their tactics to blunt each other's efforts.
Democrat and Republican committee members will likely alternate for five minutes of questions each, a format which will challenge Democrats to deliver to the television audience a coherent narrative of collusion and obstruction, while Republicans try to disrupt it and change the subject.
Democrats need to figure out how to get the cagey and disciplined Mueller to say in clear terms that Trump likely broke obstruction laws, while Republicans are expected to try and undermine his credibility.
Mueller, much-trusted in Washington circles but with a sphinx-like image, has already signalled he will be a tough nut to crack.
"Any testimony from this office would not go beyond our report," he said on May 29, as he announced the closure of the special counsel investigation.
"The work speaks for itself. And the report is my testimony."