Bob Woodward's book a work of fiction: Donald Trump

US President Donald Trump has described famed investigative journalist Bob Woodward's forthcoming book, which has some damaging revelation about his presidency, as a work of fiction.

Titled "Fear: Trump in the White House", the 448-page book is scheduled to hit stores on September 11 and claims to give an insider's account on the White House working and decision-making process in Trump's presidency.

"The book is a work of fiction. If you look back at Woodward's past, he had the same problem with other presidents. He likes to get publicity. He sells some books,” Trump said in a joint media appearance with the Amir of Kuwait inside the Oval Office on Wednesday.

The Washington Post on Tuesday had published a report along with some excerpts from the book, which the White House had said was "nothing more than fabricated stories" to make Trump look "bad".

In the book, based on hundreds of interviews, Woodward, an associate editor with the daily, has quoted senior administration officials, including Defence Secretary Jim Mattis. speaking against the president.

Trump and the White House insisted that the book does not reflect the working of the administration.

"We have done more as an administration than any other administration in already less than two years. It's incredible. We will soon be approaching two years,” Trump said.

"The book is a work of fiction. It's really, if you look at it, it was put out to interfere, in my opinion, at this time, with the Kavanaugh hearings, which I don't think it's done, because so many people have come out against it.

"So many who have been written about said I never said that. Rudy Giuliani (Trump's lead personal defense attorney) is another one. He is very insulted by the book and what was stated in the book,” the president said.

Trump said he runs a strong White House and "there's no question about it" as "we are doing things that nobody else has ever been able to do".

“Our country is stronger now than it's ever been. And in a very short period of time, USD 700 billion being spent on the military.

"The next year, USD 716 billion. We will actually be far stronger than we have ve ever been. That's what we need it to be," he said.

Trump also denied a report in the Woodward's book that he ever suggested the assassination of Syrian autocrat Bashar-al-Assad.

“Not at all. No, the book is fiction. I heard somewhere where they said the assassination of President Assad by the United States. Never even discussed,” he said.

“The book is total fiction, just like he wrote in the past about other presidents. You look at what he said about President Bush, what he said about President (Barak) Obama. Big, scandalous thing. It lasts for about a day,” he said.

"That was never even contemplated, nor would it be contemplated. And it should not have been written about in the book. It's just more fiction," Trump said.