US President Donald Trump has taken top US infectious disease expert Anthony Fauci to task about the dangers of reopening the economy and schools too quickly.

“To me it’s not an acceptable answer, especially when it comes to schools,” Mr Trump said when asked about Dr Fauci’s warnings to US senators on Tuesday (local time) about the risks of reopening the schools and economy too soon.

Dr Fauci, who directs the National Institute of Allergy and Infectious Diseases, also warned that a premature lifting of lockdowns could lead to additional outbreaks of the deadly coronavirus, which has killed more than 82,000 people in the US and brought the economy to its knees.

Mr Trump, in contrast, said on Wednesday the only thing that would be acceptable would be professors or teachers “over a certain age” not holding classes.

“I think they ought to take it easy for another few weeks,” he added.

The President, who previously made the strength of the economy central to his pitch for re-election in November, has encouraged states to reopen businesses and schools that were closed to halt the spread of the highly contagious respiratory disease.

Dr Fauci, 79, an expert in infectious diseases who has led the NIAID since 1984, has been Mr Trump’s most prominent scientific adviser throughout the crisis.

A proponent of the lockdowns, Dr Fauci has become a target for criticism from the American far right and online conspiracy theorists since he made statements about the outbreak that were at odds with Mr Trump’s.

In April, Mr Trump retweeted a call to fire Dr Fauci, after the doctor said lives could have been saved if the US had shut down sooner, spurring speculation the doctor’s days in the administration could be numbered.

Sorry Fake News, it’s all on tape. I banned China long before people spoke up. Thank you @OANN https://t.co/d40JQkUZg5

— Donald J. Trump (@realDonaldTrump) April 12, 2020

“Anthony is a good person, a very good person. I’ve disagreed with him,” Mr Trump said in an interview earlier on Wednesday with Fox Business Network’s Mornings with Maria, repeating his refrain that the country must reopen.

“We want to do it safely, but we also want to do it as quickly as possible. … We have to get it open. I totally disagree with him on schools,” Mr Trump said.

Asked about Mr Trump’s comments, New York City Mayor Bill de Blasio told CNN that Dr Fauci was “sounding an honest voice of caution and I share his view”.

“I think we have to be very careful about the steps we take.”

Mr Trump also said on Wednesday a $US3 trillion-plus coronavirus relief package proposed by Democrats in the US House of Representatives was dead on arrival.

The Democratic proposal, which includes funding for states, businesses, food support and families, was quickly rejected by Mr Trump’s fellow Republicans in the US Senate after it was unveiled on Tuesday.

-with agencies