The head of America's Centers for Disease Control and Prevention has accused Donald Trump's latest coronavirus adviser of giving the president "false" information.
Dr Robert Redfield, the CDC director, who sits on the White House coronavirus task force, was overheard on the phone criticising Dr Scott Atlas, Mr Trump's new adviser.
He reportedly suggested Mr Trump was getting inaccurate information on issues such as the efficacy of masks, how the virus affects young people, and herd immunity.
"Everything he says is false," Dr Redfield was overheard saying on a flight from Atlanta to Washington, NBC News reported.
Dr Redfield later confirmed he had been talking about Dr Atlas, a neuroradiologist who joined the task force last month and has been praised by the president.
In a statement the CDC said: "Dr. Redfield was having a private discussion regarding a number of points he has made publicly about Covid-19."
Dr Atlas responded in a statement, saying: "Everything I have said is directly from the data and the science. It echoes what is said by many of the top medical scientists in the world, including those at Stanford, Harvard, and Oxford."
A White House official said the president "consults with many experts who sometimes disagree with one another."
Later, in a television interview, Dr Redield gave a grim assessment of the pandemic. He said: "We're nowhere near the end."
He has previously been rebuked by the president over pessimistic statements about the coronavirus recovery.
It came as Dr Anthony Fauci, America's leading infectious diseases expert, said: "We're not in a good place. I hope not but, we very well might start seeing increases in deaths."
Dr Fauci specifically discussed a decision by Florida to fully reopen restaurants and bars.
He said: "That is something we really need to be careful about."
In the United states more than 200,000 people have now died and there have been seven million cases.
Some experts have warned of a coming surge in the autumn and winter months.
The number of weekly cases is growing by at least 10 per cent in 21 of the 50 states.