President Donald Trump reportedly lied, contradicted himself, and burst out in anger during a mock interview with his lead attorney in preparation for a possible sit-down interview with special counsel Robert Mueller.

The episode was recounted in an excerpt of an explosive forthcoming book about the Trump administration written by Pulitzer Prize-winning investigative journalist Bob Woodward.

Trump's lawyers are still negotiating the terms of a possible interview with Mueller.

President Donald Trump couldn't get through a mock interview in preparation for a possible sit-down with the special counsel Robert Mueller without lying, contradicting himself, and eventually exploding in anger, according to a new book from Washington Post editor and legendary investigative journalist Bob Woodward.

The previously unreported episode is described in the book "Fear: Trump in the White House," which the Post reported on Tuesday. Trump's former lead attorney John Dowd, who left Trump's legal team in March, reportedly did a practice session with Trump in January for the possible Mueller sit-down to "prove his point" that Trump would perjure himself.

After Trump couldn't adequately answer a series of rapid-fire questions Dowd asked him about the Russia investigation, the president "lost his cool," according to the Post and Woodward.

"This thing's a goddamn hoax," Trump reportedly exclaimed, launching into a "30-minute rant" before he said, "I don't really want to testify."

"Fear" is based on "hundreds of hours" of interviews Woodward had with administration officials, government documents, and notes.

The book also recounts a meeting between Dowd and Trump lawyer Jay Sekulow with Mueller in which Dowd reportedly cited the disastrous practice session as a reason why Trump could not be interviewed.

John Dowd. Thomson Reuters

"I'm not going to sit there and let him look like an idiot," Dowd is quoted as telling Mueller. "And you publish that transcript, because everything leaks in Washington, and the guys overseas are going to say, 'I told you he was an idiot. I told you he was a goddamn dumbbell. What are we dealing with this idiot for?'"

Later that month, Dowd reportedly told Trump: "Don't testify. It's either that or an orange jumpsuit."

When Trump protested Dowd's concerns, claiming he would be a "real good witness," Dowd reportedly contradicted that and said, "Mr. President, I'm afraid I just can't help you."

Dowd resigned the day after that exchange, according to the book.

The White House and Dowd did not immediately respond to Business Insider's requests for comment on the book.

A Trump-Mueller interview is still up in the air

Trump's legal team and the special counsel's prosecutors have been engaged for several months in unsuccessful negotiations over the terms of a possible voluntary interview with Trump.

Lawyers for Trump, including lead attorney Rudy Giuliani, have claimed that allowing Trump to participate in such an interview would be sending him into a "perjury trap," a claim former federal prosecutor Roland Riopelle called "legally discredited" in an August interview with Business Insider.

The Washington Post reported in March that during one failed negotiation, Mueller threatened to issue a subpoena ordering Trump to testify before a grand jury if he did not agree to a voluntary interview.

While Giuliani has told Business Insider that he plans to fight such a subpoena "before the Supreme Court," legal and constitutional experts have expressed doubt that Trump would be able to successfully quash it based on previous precedent set by the Supreme Court requiring Richard Nixon to comply with a grand jury subpoena.

Bob Woodward's "Fear: Trump in the White House" is set to be published by Simon & Schuster on September 11.