President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE lashed out at aides during a practice interview earlier this year intended to prepare him for a possible sit-down with special counsel 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, according to a new book from veteran journalist Bob Woodward.

The Washington Post, which obtained a copy of the book, reported Tuesday that former Trump attorney John Dowd arranged a mock interview for Jan. 27. As Dowd rattled off a series of questions about the investigation into Russian interference in the 2016 election, Trump reportedly stumbled over his answers and contradicted himself.

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“This thing’s a goddamn hoax,” Trump said, sparking a 30-minute rant.

“I don’t really want to testify," he concluded, according to the book.

The book goes on to describe Trump's paranoia about the Russia probe as unrelenting, with the president telling aides that "everybody's trying to get me," after Mueller was appointed in May 2017.

Woodward, who is best known for his work investigating the Watergate scandal of the Nixon administration, wrote his latest book based on hundreds of hours of interviews with firsthand sources, meeting notes, personal diaries, files and documents.

The book — "Fear: Trump in the White House" — is set to be released on Sept. 11.

Trump frequently blasts the Mueller investigation as a "witch hunt" and a "hoax." He has recently alleged that the special counsel has conflicts of interest, and told Bloomberg News in an interview last week that he believes the probe is "illegal."

The president and his legal team have given mixed statements on whether Trump will sit for an interview with Mueller. After publicly declaring on multiple occasions that he would be willing to testify for Mueller, the president's attorneys have since expressed skepticism that such an interview will take place.