Dr. Anthony Fauci warned Thursday that taking too "accusatory" a tone with China over investigating origins of the coronavirus could lead the communist government to be even more reticent to share information.

MSNBC's Willie Geist wondered why it was so difficult to find the true origins of the virus. Geist asked Fauci if China being "so opaque" had played a role.

"I mean, it’s obviously in China’s interest to find out exactly what it is, and the ‘is’ of the natural theory would be to find that link, so you have to keep looking for it," Fauci said. "I mean, obviously you want openness and cooperation. One of the ways you can get it is don’t be accusatory. Try to get both a forensic, a scientific, and an investigational approach. I think the accusatory part about it is only going to get them to pull back even more."

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Fauci said it would take "people of good faith" trying to find the true origin and  repeatedly encouraged people to keep an open mind.

Asked by Geist if it would make sense for China to cover up a lab leak or something more nefarious, Fauci said he didn't want to speculate.

"It'll go into the Twitter world like crazy," he said. "I'm going to leave that to other people and not surmise and guess whose interest it is. It's not helpful."

Fauci told MSNBC he still felt it was "more likely" the virus had originated naturally, even as the theory it leaked from a lab has been increasingly considered anew by the same experts and media who once dismissed it. A recent report showed three researchers at the Wuhan Institute of Virology had COVID-like symptoms in November 2019.

President Joe Biden ordered the intelligence community last week to investigate the virus's origins. 

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"We still don't know what the origin is," Fauci said, discussing the previous dismissal of the lab leak idea as a conspiracy theory. "The fact that it could have been something else clearly was there."

CNN last year wrote Fauci had "crushed" former President Donald Trump's lab origin theory on the coronavirus when Fauci told National Geographic he was "very strongly leaning toward this could not have been artificially or deliberately manipulated."

An email released this week revealed Fauci being thanked last year by Peter Daszak of the EcoHealth Alliance for pouring cold water on the the lab-leak theory. Daszak's organization funded research at the Wuhan Institute of Virology on bat coronaviruses, partly through taxpayer grant money from Fauci's National Institute of Allergy and Infectious Diseases.

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"I just wanted to say a personal thank you on behalf of our staff and collaborators, for publicly standing up and stating that the scientific evidence supports a natural origin for COVID-19 from a bat-to-human spillover, not a lab release from the Wuhan Institute of Virology," Daszak said in an email. Fauci replied: "Many thanks for your kind note."

Fox News' Tyler Olson contributed to this report.