Dr. Anthony Fauci on Monday rejected President Donald Trump’s recent criticism of him in which he called the infectious disease expert an “alarmist.”

“I consider myself a realist, as opposed to an alarmist,” Fauci said in an interview on Instagram Live with Maria Schriver.

Asked if Trump’s characterization of him was unfair, Fauci said, “I believe so, but then again, others have different opinions.”

“I’m a realist but I’m also an optimist,” added Fauci, the director of the National Institute of Allergy and Infectious Diseases.