President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE on Wednesday morning lashed out in frustration over Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's testimony to Congress just hours before the former special counsel was set to appear on Capitol Hill.

The president tweeted multiple times about Mueller late Tuesday and early Wednesday, signaling an agitation with the highly anticipated public spectacle that could cast another cloud over his presidency.

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"So Democrats and others can illegally fabricate a crime, try pinning it on a very innocent President, and when he fights back against this illegal and treasonous attack on our Country, they call It Obstruction?" Trump tweeted. "Wrong! Why didn’t Robert Mueller investigate the investigators?"

So Democrats and others can illegally fabricate a crime, try pinning it on a very innocent President, and when he fights back against this illegal and treasonous attack on our Country, they call It Obstruction? Wrong! Why didn’t Robert Mueller investigate the investigators? — Donald J. Trump (@realDonaldTrump) July 24, 2019

Leading up to the testimony, Trump has focused on the late confirmation that one of Mueller's top deputies will accompany him as an adviser during his testimony.

The president said late Tuesday that the move was "very unfair" and "should not be allowed" and on Wednesday asserted he would not have agreed to such terms.

Trump's approval is not needed for the committee's hearing format.

"It was NEVER agreed that Robert Mueller could use one of his many Democrat Never Trumper lawyers to sit next to him and help him with his answers," the president tweeted. "This was specifically NOT agreed to, and I would NEVER have agreed to it. The Greatest Witch Hunt in U.S. history, by far!"

It was NEVER agreed that Robert Mueller could use one of his many Democrat Never Trumper lawyers to sit next to him and help him with his answers. This was specifically NOT agreed to, and I would NEVER have agreed to it. The Greatest Witch Hunt in U.S. history, by far! — Donald J. Trump (@realDonaldTrump) July 24, 2019

The president reasserted his claim that Mueller interviewed to be FBI director before being appointed special counsel, suggesting it would be perjury for him to say otherwise. Trump has used the issue to suggest Mueller was conflicted in his investigation.

However, Mueller's report addressed the claim. Former White House chief strategist Stephen Bannon told federal investigators that Mueller did not go to the White House seeking to become FBI director for a second time and was instead invited to offer “a perspective on the institution” to the president.

....interview, including the Vice President of the United States! — Donald J. Trump (@realDonaldTrump) July 24, 2019

Trump later questioned why Mueller did not investigate himself, as well as 2016 Democratic nominee Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE and several Justice Department officials.

So why didn’t the highly conflicted Robert Mueller investigate how and why Crooked Hillary Clinton deleted and acid washed 33,000 Emails immediately AFTER getting a SUBPOENA from the United States Congress? She must have GREAT lawyers! — Donald J. Trump (@realDonaldTrump) July 24, 2019

Mueller's testimony begins at 8:30 a.m. on Wednesday. He will appear first before the House Judiciary Committee, followed by the House Intelligence Committee.

The anticipation of the hearings dominated cable news coverage early in the week, and the spectacle is expected to draw a large audience on Wednesday.

The former special counsel had been reluctant to testify and has said his testimony would not veer from his 448-page report that did not establish a conspiracy between the Trump campaign and the Russian government, and neither implicated nor exonerated the president on obstruction of justice charges.

Trump has attempted to project indifference in the days leading up to Mueller's testimony but has revealed the appearance does have his attention. He insisted last week he would not be watching, but on Monday said he "might" watch at least part of the hearing and renewed attacks on Mueller's credibility.

The president's public schedule is open during the hearings up until 4 p.m., when he is scheduled to leave the White House for a fundraiser in West Virginia.

Bookmark The Hill to follow live coverage of Mueller's testimony.

Updated at 7:58 a.m.