President Trump on Wednesday blasted former Special Counsel Robert Mueller’s scheduled hearing before the House Judiciary and Intelligence committees as a “diversion,” claiming the spectacle is meant to draw attention away from alleged wrongdoing on "the other side."

Speaking to reporters at the White House’s South Lawn before departing for a trip to Japan, Trump brushed aside concerns that Mueller’s testimony on July 17 will reveal more information than what was already laid out in the report.

“This is really a hoax, the worst political scandal is on the other side,” Trump said of the Democrats. “My only response to Mueller is ‘does it ever stop?’ This is a diversion.”

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Mueller's rare testimony, secured after a subpoena, in front of the House Judiciary and Intelligence committees is likely to be the most highly anticipated congressional hearing in years, particularly given Mueller's resolute silence throughout his two-year investigation into Russian contacts with Trump's campaign. Democrats negotiated for more than two months to obtain the testimony, hoping to focus public attention on the special counsel's 448-page report that they believe most Americans have not read.

"I think just if he says what was in the report and says it to the American people so they hear it, that will be very, very important," Judiciary Committee Chairman Jerrold Nadler told reporters Wednesday. "Whether he goes further than that, we'll see."

There is also a more than reasonable chance that by the time of Mueller’s testimony, the Justice Department inspector general could release his highly anticipated report on the FBI’s use of the Foreign Intelligence Surveillance Act (FISA) system in the early stages of the Russia probe. If that happens, Trump's Republican allies who have long alleged FBI abuses as part of that process are sure to weaponize the report going into the hearings -- and could be poised to turn the tables on majority Democrats.

Fox News has learned Mueller would appear only under a subpoena, which has been described as a "friendly" subpoena, one that in essence had been planned. Mueller is expected to stick to the "four corners" of his report.

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Fox News also was told the Democrats did not tell Republicans about the Mueller subpoena, and most Republican lawmakers found out on the House floor or from reporters.

Democrats say it is now the job of Congress to assess the report's findings. Almost 80 Democrats have already announced that they believe an impeachment inquiry is needed, or around a third of the caucus. But House Speaker Nancy Pelosi has preferred a methodical approach that includes testimony from witnesses like Mueller. Supporters of opening the impeachment process hope that his open testimony will help galvanize their effort.

Democrats are likely to confront the special counsel on why he did not come to a firm conclusion on obstruction of justice, seek his reaction to Trump's criticism and ask for his personal opinion about whether Trump would have been charged were he not the commander in chief. Republicans are likely to ask him about how the probe was conducted, and whether there was bias against Trump at the Justice Department.

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House Republicans likely will try to press Mueller on anti-Trump text messages between former FBI Agent Peter Strzok and attorney Lisa Page and on an anti-Trump dossier authored by British ex-spy Christopher Steele. Democrats likely will ask about how Mueller reached his conclusion not to charge Trump and if there was pressure by Attorney General Bill Barr not to go after Trump more forcefully.

Barr said previously that he had no problem with Mueller testifying and would not stand in the way.

In the report issued in April, Mueller concluded there was not enough evidence to establish a conspiracy between Trump's presidential campaign and Russia, which was the original question that started the investigation. But he also said he could not exonerate Trump on obstruction of justice.

Fox News’ Louis Casiano and The Associated Press contributed to this report.