Woodward's book is based on "deep background" interviews, which he defines in his book as interviews where "all the information could be used but I would not say who provided it".
Woodward said he tried multiple times to interview Trump for the book, but was rejected.
Kelly last week also denied quotes attributed to him in the book in which he allegedly said that Trump was "unhinged" and "an idiot" whose administration had turned into "Crazytown".
Sanders added that there has been no discussion within the White House about administering lie detector tests to find out who is responsible for the New York Times opinion piece, in which a senior administration official described a Trump administration mired in dysfunction, with aides disparaging the Republican president and working to prevent him from making disastrous decisions.
Several administration officials, including Defense Secretary James Mattis and chief of staff John Kelly, have denied the anecdotes and quotes ascribed to them in Woodward's book.
"The people are not anonymous to me", he says of his sources. One of the most unsafe incidents involved Trump's obsession with the 28,000 troops the US has stationed in South Korea, and the $3.5 billion a year the USA pays to keep them there, Woodward explained, quoting Trump as saying: "I don't know why they're there. The snakes are everywhere but we're getting rid of them, '" a person close to Trump told Axios.
"You can, in an nearly microscopic way, establish what occurred - and that's what I've done in this book".
Trump talked about raising taxes on the rich repeatedly during his campaign for the presidency, and former Trump adviser Steven Bannon reportedly advocated for a top rate of 44 percent on people who earn more than $5 million a year as he pushed for a more populist version of the tax legislation. As a result, Cohn kept the president from jeopardizing a top-secret intelligence operation that would allow the U.S.to detect intercontinental ballistic missiles launched from North Korea.
"We're underestimating how serious all of this is", Woodward tells NPR.
In early 2018, Trump sent several belligerent tweets that seemed created to taunt North Korean leader Kim Jong Un.
"The Woodward book is a Joke".
On Woodward's book, which will be released on Tuesday, Sanders reiterated the that numerous sources quoted in the book have denied what the Washington Post journalist reported and called Woodward's book "careless" and "reckless".
Weeks after Trump considered sending that tweet, Woodward writes, the president asked the National Security Council: "What do we get by maintaining a massive military presence in the Korean peninsula?" Asked whether he has tape recordings of most of the interviews, Woodward said yes.
It was the first White House briefing since the New York Times essay became public last week.
"I don't know who it is", Woodward says.
Sanders fired back: "I think we would say that it's about as ridiculous as most of Bob Woodward's book".