Washington CNN  — 

Dr. Anthony Fauci said Friday that the lack of truthfulness from the Trump administration regarding the Covid-19 pandemic “very likely” cost American lives.

“Particularly when you’re in the situation of almost being in a crisis with the number of cases and hospitalizations and deaths that we have – when you start talking about things that make no sense medically and no sense scientifically, that clearly is not helpful,” Fauci, the chief medical adviser to President Joe Biden, said on CNN’s “New Day” Friday.

Asked by CNN’s John Berman if the lack of candor over the last year and lack of facts, in some cases, cost lives, Fauci said, “You know, it very likely did.”

He warned that it’s “not helpful” when “you’re starting to go down paths that are not based on any science at all,” adding that he doesn’t wish to rehash the ways in which the Trump administration steered away from science.

Fauci, who sat on former President Donald Trump’s coronavirus task force, said Thursday that the Biden administration’s approach to handling the Covid-19 pandemic will be “completely transparent, open and honest” with the American people.

“If things go wrong, not point fingers but to correct them. And to make everything we do be based on science and evidence,” he told reporters Thursday during a White House briefing.

Fauci, who is also the director of the National Institute of Allergy and Infectious Diseases, had disagreed with Trump on how to approach the pandemic, with the former president consistently downplaying the threat of Covid-19. Trump attacked Fauci publicly and had suggested at one point he was considering firing him, and by the end of the Trump administration, Fauci was largely sidelined.

Fauci admitted Thursday that it was “uncomfortable” when things like hydroxychloroquine were promoted as treatments for Covid-19 when they weren’t based on fact, and that he takes “no pleasure at all in being in a situation of contradicting the President.”

He called it a “liberating feeling” to now be able to “talk about what you know, what the evidence, what the science is,” without fear of repercussions.

CNN’s Kevin Liptak contributed to this report.