One of Italy's leading experts on the coronavirus warned U.S. President Donald Trump on Wednesday that he would be making a "disastrous" mistake if he were to fire Dr. Anthony Fauci.

Fauci, the director of the National Institute of Allergy and Infectious Diseases, is the top U.S. public health official on the coronavirus emergency.

His position has looked shaky after suggesting that an earlier lockdown in the U.S. could have saved more lives and after Trump retweeted a post with the #FireFauci hashtag.

Firing Fauci "would be disastrous news not only for the United States but for the whole international community," professor Giuseppe Ippolito wrote in a public letter.

Ippolito is the scientific director of the Spallanzani hospital in Rome, Italy's top medical research and treatment center for infectious diseases.

He praised his U.S. colleague as "one of the most important scientists in the world in the field of infectious diseases," and "a guide and a world reference point in all health emergencies of the last three decades and more."

"We need Anthony Fauci's leadership, in the U.S. or elsewhere, to tackle the challenges this pandemic poses to our health systems," Ippolito said.

The Spallanzani would be "honored" to have Fauci as an adviser, and Italian public authorities could "benefit (from) his great vision and expertise," the Italian virologist said.

Ippolito addressed his public letter, written in Italian and English, to President Sergio Mattarella. It was not clear whether it represented an actual job offer to Fauci in case he is dismissed.