Peter Navarro, a trade adviser to President Donald Trump, claimed that Dr Anthony Fauci is "wrong about everything" as the White House steps up its bid to discredit its own top infectious diseases expert.
"Dr. Fauci has a good bedside manner with the public but he has been wrong about everything I have ever interacted with him on," Navarro said in a statement to The Washington Post for a story about Fauci being sidelined.
He continued: "Now Fauci is saying that a falling mortality rate doesn't matter when it is the single most important statistic to help guide the pace of our economic reopening. So when you ask me if I listen to Dr. Fauci's advice, my answer is only with caution."
The president has claimed that a continuing decline in the proportion of the US population dying from the coronavirus is proof that his strategy has worked, despite an alarming increase in infections.
But in a live-stream press conference last week Fauci warned that "It's a false narrative to take comfort in a lower rate of death."
"There's so many other things that are very dangerous and bad about this virus, don't get yourself into false complacency."
Last week, the death rate began to climb in several US states for the first time in several months. There is usually a lag between an increase in infections and death rates.
Navarro's statement Sunday came as the White House began circulating a list of mistakes committed by Fauci to news outlets, in a seeming bid to undermine one of the most trusted US government officials.
In recent weeks Fauci has delivered blunt assessments of US failings in response to the coronavirus, calling for states where infection rates are climbing to reintroduce restrictions.
His statements have contrasted with the upbeat message that Trump has delivered as he seeks to stimulate the US economy ahead of November's presidential election.
Navarro has long called for the government to rapidly lift the restrictions advocated by public health officials such as Fauci, He warned in an interview with The New York Times in April that the damage done by the lockdown could ultimately exceed that of the virus.
Navarro is one of several White House officials to lobby against Fauci, according to the Post. The two fell out, according to the report, over the anti-malarial drug hydroxychloroquine, which Trump and Navarro touted as a coronavirus cure.
Fauci, in public statements and internally, refused to endorse it, saying it had not been proven to be effective.
The Food and Drugs Administration withdrew its permission for the drug to be used to treat emergency patients after studies found it was dangerous for some, particularly those with underlying heart conditions.
Navarro, a China hawk, has also been accused of spreading political misinformation about the virus, claiming that China sought to deliberately spread the illness.