Bob Woodward's upcoming book offers new insights into President Donald Trump's anger over advisers' efforts to clean up his explosive "both sides" remark on the violence last year at a white supremacist rally in Charlottesville, Virginia.

The Pulitzer Prize-winning author's new book , "Fear: Trump in the White House," is being released September 11. CNN obtained a copy.

Trump's August 2017 remarks concluding there was "blame on both sides" for the violence was a stunning moment early in his presidency that ignited a backlash over his views on race and consumed the White House for days. The new revelations may reopen that debate.

In the book, Woodward describes how then-White House staff secretary Rob Porter worked with Trump to write a second speech to try to repair his initial comments about violence at the marches.

Porter tried to convince the President he needed to clarify his remarks. But Trump appeared to resist, according to the book, repeatedly saying: "I don't know about this. ... This doesn't feel right to me."

Eventually, Trump agreed, and two days later in a televised speech he denounced racism, the "KKK, neo-Nazis, white supremacists and other hate groups." Woodward describes how White House aides were relieved, and chief of staff John Kelly encouraged staff to tell the President what a good job he did.

But then Trump turned on the TV.

One Fox News commentator gave Trump praise but also added, "That's almost an admission of 'Okay, I was wrong.'" Then Fox News correspondent Kevin Corke said: "Some 48 hours into the biggest domestic challenge of his young presidency, Mr. Trump has made a course correction."

Trump exploded at the coverage, Woodward reports. "That was the biggest fucking mistake I've made," the President told Porter. "You never make those concessions. You never apologize. I didn't do anything wrong in the first place. Why look weak?"

Trump continued venting to Porter, Woodward writes. "I can't believe I got forced to do that," he said. "That's the worst speech I've ever given. I'm never going to do anything like that again."

One day later, Trump spoke at an unrelated Trump Tower event, where he surprised his staff and doubled down on his original sentiment that "both sides" were to blame for the violence, equating white supremacists with what he termed the "alt-left."

"You had a group on one side that was bad and you had a group on the other side that was also very violent," Trump said. "Nobody wants to say it, but I will say it right now."

Porter was shocked, Woodward writes, and told Trump he thought the second speech was the only good one.

"I don't want to talk to you," Trump responded. "Get away from me."

The White House accused Woodward on Tuesday of spreading "fabricated stories" about Trump but did not rebut any of the specific claims in the book about Charlottesville.

"This book is nothing more than fabricated stories, many by former disgruntled employees, told to make the President look bad," White House press secretary Sarah Sanders said. "While it is not always pretty, and rare that the press actually covers it, President Trump has broken through the bureaucratic process to deliver unprecedented successes for the American people. Sometimes it is unconventional, but he always gets results."

Woodward's book relies on hundreds of hours of taped confidential background interviews and dozens of sources in Trump's inner circle, as well as documents, files, diaries and memos, including a note handwritten by Trump himself.

Woodward's reporting comes with a credibility that separates this book from previous efforts on Trump. The author and Washington Post journalist has won two Pulitzer Prizes, including one for his coverage of the Watergate scandal that led to President Richard Nixon's resignation.

The book describes a scene in the Oval Office in which then-chief economic adviser Gary Cohn tried to resign in response to Trump's comments. Trump berated Cohn, blamed his wife and "liberal Park Avenue friends," and told him: "This is treason."

Cohn eventually agreed to stay to help pass a sweeping tax bill. Kelly, who witnessed the exchange, praised the economic adviser's self-control.

"If that was me, I would have taken the resignation letter and shoved it up his ass six different times," Kelly told Cohn, according to notes Cohn made of the encounter, as reported by Woodward.

The book describes the aftermath of Charlottesville as a turning point for many in the White House.

Woodward reports that Kelly told then-White House chief strategist Steve Bannon he was afraid a third of the Cabinet could resign because "this thing's on a knife's edge ... people are not going to tolerate it." But Trump's team largely fell in line -- there were no major resignations in the wake of Charlottesville.