The US’s top infectious disease expert has said he would resign if Donald Trump retakes the presidency in 2024.

Dr Anthony Fauci bluntly said “no” when CNN’s Jim Acosta asked him during an interview on Sunday if he would want to stay on as the director of the National Institute of Allergies and Infectious Diseases in the event that voters gave Trump a second stint as president.

Fauci, 81, has led the institute since 1984, serving under seven presidents. He said he wasn’t confident in Trump’s ability to lead the country through a public health emergency like the coronavirus pandemic, and his administration’s response at the beginning of the crisis in early 2020 was “less than optimal”.

“If you look at the history of what the response was during the administration, I think at best you could say it wasn’t optimal,” Fauci said. “And I just think history will speak for itself. I don’t need to make any further comment about that – it’s not productive.”

Acosta asked Fauci whether he would want to continue working his job if Trump won a second term after losing to Joe Biden in the 2020​​​​ presidential election.

“Well, no,” Fauci said, in part.

Fauci and Trump have a history of clashing with each other. The former president and his fellow Republicans villainized Fauci for urging Americans to take various measures to protect them from spreading and contracting the virus which had killed 1 million people nationwide as of Monday, including wearing masks and getting vaccinated.

Trump was aggravated by Fauci’s frequent television appearances, calling him “not a great doctor but a great promoter”. He attacked Fauci for being skeptical of the hotly contested theory that the deadly virus escaped from a laboratory in Wuhan, China.

“He’s been wrong on almost every issue and he was wrong on Wuhan and the lab also,” Trump said once.

Fauci, in turn, criticized Trump when the former president’s unsuccessful re-election campaign took Fauci’s words that he couldn’t imagine “anyone … doing more” than federal officials in general and tried to make it look in a video like he was speaking admiringly of Trump’s handling of the coronavirus.

“I have never publicly endorsed any political candidate,” Fauci said at the time. “The comments attributed to me with my permission … were taken out of context.”

Fauci this year has said the US was out of the full blown pandemic phase of the coronavirus crisis, though cases could still rise as variants and subvariants proliferate.