U.S. President Donald Trump had been aware in early February of how deadly and contagious the novel coronavirus was, but played down the threat in public, audio recordings of interviews for a new book obtained by U.S. media showed Wednesday.

The revelations could be a blow to Trump ahead of the November presidential election as he already faces criticism for his handling of the pandemic, which has cost the lives of around 190,000 people in the United States and triggered a sharp economic downturn.

"You just breathe the air and that's how it's passed," Trump said in a Feb. 7 interview with journalist Bob Woodward, according to a recording made available by The Washington Post and CNN. "And so that's a very tricky one. That's a very delicate one. It's also more deadly than even your strenuous flus."

Before declaring a national emergency over the coronavirus outbreak on March 13, the president had largely played down the virus threat by comparing it with influenza, while asking the public to stay calm because it would "go away."

In another interview on March 19, Trump is asked by Woodward about what made him pivot on the gravity of the virus and he said, "To be honest with you, I wanted to always play it down."

"I still like playing it down, because I don't want to create a panic," he said.

Woodward, a two-time Pulitzer Prize winner, conducted 18 on-the-record interviews with the president between December and July, according to The Washington Post and CNN. Woodward's new book "Rage," set to be released next Tuesday, is based on the interviews.

Democratic presidential nominee Joe Biden immediately attacked Trump on the issue, saying the Republican president had betrayed the people by hiding the truth that the virus was more deadly than the flu.

"He knowingly and willingly lied about the threat it posed to the country for months," the former vice president said, adding, "It was a life and death betrayal of the American people."

Trump later defended the remarks he made to Woodward, telling reporters that he had to "show calm" so as not to scare the public and emphasizing that he has taken border control measures and other measures to minimize the impact of the pandemic.

According to CNN, the new book "Rage" also covers Trump's diplomacy with North Korea, with Woodward obtaining the 27 "love letters" Trump exchanged with leader Kim Jong Un, 25 of which have not been reported publicly.

In the letters, Kim flatters Trump by repeatedly calling him "Your Excellency." Kim writes in one that meeting again would be "reminiscent of a scene from a fantasy film," and in another that the "deep and special friendship between us will work as a magical force," according to CNN.

North Korean leader Kim Jong Un and U.S. President Donald Trump at the demilitarized zone (DMZ) separating the South and North Korea on June 30, 2019. (KCNA/Kyodo)

Woodward also describes in the book some tense moments when concerns grew in the United States over the possibility of a nuclear war with North Korea amid provocations in 2017.

"We never knew whether it was real," Secretary of State Mike Pompeo was quoted as saying, "or whether it was a bluff."

But it was so serious that then Secretary of Defense Jim Mattis slept in his clothes to be ready in case there was a North Korean launch and repeatedly went to a cathedral to pray, according to CNN.

Trump also reportedly boasted to Woodward about the United States developing a new secret "weapons system," the existence of which the journalist has confirmed through other sources although they did not provide further details.