(NewsNation) — Dr. Anthony Fauci said he’s kept a “completely open mind” on where COVID-19 originated, and that the attacks on him are “politically motivated.”

NewsNation’s Chris Cuomo asked Fauci, the former chief medical adviser to President Biden who led the U.S. response to COVID-19, to address critics who say he’s the target of “covering up” the source of COVID-19.

“It’s politically motivated. I don’t know what they’re talking about ‘covering up.’ I have been totally transparent throughout,” Fauci said. “I was not comfortable having to get up and contradict the president of the United States. That triggered a great deal of hostility in which I became a target, and it’s gotten worse.”

Fauci told Cuomo that no one knows definitively where or how COVID-19 evolved. He’s kept an open mind about all possibilities and discussed the two most prominent theories — a lab leak or a natural occurrence.

“Instead of arguing about it, we should do whatever we can to prevent either of those possibilities from occurring again,” Fauci said.

Since the COVID-19 pandemic began, there have been competing theories over the origins of the virus.

Fauci acknowledged the “lab leak theory,” which speculates that COVID-19 occurred as a result of work in a Chinese lab. Supporters of the theory have pointed to China’s reluctance to cooperate with investigations into the origin of the virus and a history of lax safety procedures at the facility.

The House voted unanimously Friday to declassify U.S. intelligence information about the origins of COVID-19, a sweeping show of bipartisan support near the third anniversary of the start of the deadly pandemic.

The 419-0 vote was final congressional approval of the bill, sending it to President Joe Biden’s desk. It’s unclear whether the president will sign the measure into law, and the White House said the matter was under review.

The Associated Press contributed to this report.