Anthony Fauci, former chief medical adviser to the US president, says he has "an open mind" about the origins of COVID-19, but insists it was "not engineered as a bio weapon" by China or anybody else.
Speaking on the third anniversary of the World Health Organization (WHO) declaring coronavirus a pandemic, Dr Fauci said he agreed with many leading epidemiologists that COVID-19 was likely a "natural occurrence from animal to human".
"Evolutionary virologists … wrote two very important, well-written peer-reviewed pieces in Science magazine strongly suggesting that in fact it was a natural occurrence from an animal to a human," Dr Fauci told Jim Acosta on CNN.
"But [while they] strongly suggest it, it doesn't nail it down definitively and that's the reason I say to do this day I will keep a completely open mind as to what the original [cause] is."
COVID-19 has caused almost 7 million deaths globally since was first detected in the Chinese city of Wuhan in December 2019.
Dr Fauci, a key advisor on the US Coronavirus Task Force under then-president Donald Trump when COVID-19 was declared a pandemic in March 2020, said any sinister origins of COVID-19 had effectively been ruled out after numerous investigations.
"One of the things that people maybe don't really appreciate is that all of the intelligence agencies agree unanimously that this was not engineered, namely they didn't deliberately do this to make a bio weapon," Dr Fauci said.
"Everybody agrees with that no matter what your prior thoughts were."
Dr Fauci, long considered his nation's top diseases expert, came under attack during a hearing in the House of Representatives in Washington last week. Republicans claimed he had promoted the view that an infected animal spread the virus to humans to deflect attention from US-sponsored research at China's Wuhan Institute of Virology.
At the hearing, former Center for Diseases Control (CDC) director Robert Redfield accused Dr Fauci of freezing him out a high-level phone call among experts during the early stages of the pandemic in 2020 "because they wanted a single narrative and I obviously had a different point of view".
Dr Redfield suspected that coronavirus had leaked from a Chinese lab rather than being transmitted from bats in a Wuhan food market.
Dr Fauci rejected Dr Redfield's claims of bias against him as "completely untrue", adding that other people on the call had the opinion that COVID-19 might have been an engineered virus.
While he does not believe the virus was concocted artificially, Dr Fauci acknowledged that it was still possible that COVID had leaked from a lab as part of "a natural occurrence".
"A lab leak could be that someone was out in the wild, maybe looking for different types of viruses in bats, got infected, went into a lab and was being studied in a lab and then came out of the lab," Dr Fauci said.
"If that's the definition of a lab leak, then that is still a natural occurrence.
"The other possibility is that someone takes a virus from the environment that doesn't actually spread very well in humans then manipulates it a bit and accidentally it escapes and accidentally infects someone and you get an outbreak.
"[But] there are no lab leaks that have led to pandemics."
Dr Fauci, 82, who was accused by Mr Trump in 2020 of making "a lot of mistakes" in his handling of coronavirus, stepped down from his role as chief medical adviser to President Joe Biden last December.
He has long been the target of anti-vaxxers who blame him for the vaccine mandates imposed by some US states during the height of the COVID-19 outbreak.
