U.S. President Donald Trump pushed for schools to reopen and sharply disagreed with the nation's top infectious disease expert, who warned this week against sending students back to class too soon.

"We have to get the schools open, we have to get our country open," Trump said in an interview with Fox Business aired on Thursday.

"I totally disagree with him on schools," the president said of Anthony Fauci's words of caution at a Senate hearing earlier in the week.

Fauci told lawmakers there would have to be a "step-by-step" assessment of whether the dynamics of the outbreak would be right for schools to reopen in the autumn, and noted no vaccine would be available for use by then.

Fauci, who is one of the most prominent faces on Trump's coronavirus task force, also warned of the dangers to children of a virus that doctors are still struggling to understand.

"I think we better be careful [that] we are not cavalier in thinking that children are completely immune from the deleterious effects," he said, pointing to cases of a dangerous inflammatory syndrome in very young coronavirus patients.

Trump downplayed the risks of the virus to children in the interview.

"I think we have to open our schools, young people are very little affected by this," he said.

On Wednesday, Trump said Fauci had not given "an acceptable answer" in his congressional testimony.

The president has been eager to reopen schools and businesses to restart the economy as soon as possible and has often clashed with the guidance of health officials.