Ron Kessler, investigative reporter and author of "Inside the Trump White House," said President Donald Trump is fit to hold the office of the presidency, contradicting the controversial new book by Michael Wolff.

"My book is about unique access to Trump and his aides. In fact, I interviewed him last weekend the night before the Mar-a-Lago New Year's Eve party and he was perfectly normal, on top of everything," Kessler told Bill Tucker on Newsmax TV's "Newsmax Now."

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Kessler said he had been told former White House chief strategist Steve Bannon, who criticizes Trump's administration in Wolff's expose, "Fire and Fury: Inside the Trump White House," was "pushing the book" and maintained he had "set up the whole thing."

"I do know that it was Bannon who, according to Sarah Huckabee Sanders as well, was pushing the book. I know from Bannon that he set up the whole thing. He got people to cooperate, so he did have real interviews in some cases," Kessler said.

Kessler explained that in researching his new book on Trump's presidency that's due out in the spring, he would also detail information about Wolff's book that has stirred such controversy.

"I will be going into (Wolff's book) with the inside story about how that book was done," adding there was "a personal experience that I can share with you about the book."

"The book says that Bannon thought that what Trump said about Charlottesville being decent people on both sides was a sign that he may be mentally unfit and that the 25th Amendment could be invoked to remove him from office. Well, it so happens that I was in the White House with Bannon during that time interviewing him for my book.

"It was right in the middle of Trump making these statements and Bannon was gleeful. He thought it was wonderful what Trump was saying and he told me that he had talked with him twice, at least twice, on the phone.

"Bannon said that he advised him not to back down, not to take back what he had said, not to try to revise it, because he said the press will only say it's too little, too late. So, he was 100 percent, not only 100 percent for what Trump was saying, but actually urged him on probably" Kessler explained.

Kessler predicted the controversy about Wolff's book would soon "blow over" and people would "recognize that it's not an honest story."

In his new book, "Inside the Trump White House," Kessler maintained it would be "the real story of Trump and his presidency, and it's something that you can bank on."

"(Trump) said that this interview that he's giving me is the only interview he is doing for a book or will do for a book," Kessler said.