(NewsNation) — Dr. Anthony Fauci said he was put in an “uncomfortable position” while tasked with delivering COVID-19 information during the Donald Trump administration.

Fauci, the nation’s top infectious disease expert and chief medical adviser for the White House, is due to retire in December.

Appearing Thursday on NewsNation’s “CUOMO,” Fauci recounted the lessons learned from the nation’s early COVID-19 response. While he claimed the former president made statements about the virus that “were just not true,” Fauci stood firm that all the chief medical adviser recommendations were rooted in science, not politics.

“You had a mixture of the president trying to answer medical questions and my standing there and being put in the uncomfortable position … of when he said something that absolutely was not correct to have had to publicly correct him,” Fauci said. “I did not relish that because I have a great deal of respect for the office of the presidency.”

Fauci also defended the COVID-19 lockdowns that took place early on in the pandemic, saying they “saved lives” while hospitals were being overrun.

“The only way you stop that is by essentially stopping the virus in its tracks,” he said.

With the benefit of hindsight, “We would have been much more strict in demanding mask wearing,” Fauci said.

“What we know now about this virus, or we did not know in January, February and March of 2020,” Fauci said, “we did not know about the fact … of aerosol transmission or that people who had no symptoms were the main spreaders of the virus.”

Recommendations to close schools and enforce shelter-in-place orders early during the pandemic were celebrated by some and criticized by others, but those decisions weren’t made lightly, Fauci said.

“We said that we’ve got to do everything we can to keep the kids in school, but to protect them while they’re in school by surrounding them with people who were vaccinated, getting good ventilation in the schools,” Fauci said. “That’s what we were talking about. Now, that was before children were allowed to get vaccinated. No one wants to keep the children out of school. We’re totally aware of the real and potential negative consequences on the children, but you make a serious decision like that in order to save lives.”

Looking forward, much remains unknown about the longer term effects of COVID. In that regard, learning more about the lasting effects of what’s sometimes referred to as long-haul COVID is of “profound urgency,” Fauci said.

“The problem is we don’t know or understand what the underlying pathogenic mechanisms of it is,” Fauci said. “Is it a reality? You bet … The laboratory data appear to be normal, yet someone is profoundly fatigued.”