US President Donald Trump has said a sobering warning by his top infectious diseases expert about lifting pandemic restrictions too soon was unacceptable.
He accused Dr Anthony Fauci of wanting "to play all sides of the equation" in his testimony to lawmakers on Tuesday.
The president said he was especially dissatisfied with Dr Fauci's caution around reopening schools too quickly.
Covid-19 has infected nearly 1.4 million people in the US and killed 84,000, while ravaging the economy.
What did the US president say?
Speaking on Wednesday at the White House, Mr Trump took issue with Dr Fauci's comments to a Senate hearing a day earlier about the risks to children of reopening and his assessment that a vaccine was unlikely before classes could begin this autumn.
"Look, he wants to play all sides of the equation," Mr Trump said of his top coronavirus expert's concerns.
"I was surprised by his answer actually, because, you know, it's just to me - it's not an acceptable answer, especially when it comes to schools," the president told reporters.
He said "the only thing that would be acceptable" is giving older teachers and professors a few more weeks before they return.
"Because this is a disease that attacks age, and it attacks health," the president said.
"But with the young children, I mean, and students, it's really - just take a look at the statistics. It's pretty amazing," Mr Trump added.
The Republican president is keen to get Americans back to work and has praised governors who are moving to do so while criticising others for not acting aggressively enough.
The country is split over Mr Trump's focus on protecting livelihoods, critics accuse him of gambling with lives to serve his own political interests ahead of November's re-election bid.
The president's latest comments come amid reports of some young children being severely affected by an inflammatory syndrome that could be linked to the virus.