President Trump’s two top coronavirus advisors “argued strongly” with him on Sunday against easing social isolation guidelines, successfully convincing him instead to extend them until at least the end of April, the government’s top infectious disease expert Dr. Anthony Fauci said Monday.

Fauci told CNN’s John Berman that he and White House coronavirus response coordinator Deborah Birx told President Trump in the Oval Office on Sunday that easing off the self-isolation measures early would only allow COVID-19 the space to rebound, killing more people and perhaps hurting the economy too.

“That’s the reason why we argued strongly with the President that he not withdraw those guidelines after 15 days, but that he extend them,” Fauci said. “And he did listen.”

On Sunday evening, Trump announced that guidelines advising against non-essential travel and gatherings of more than 10 people would continue through April, marking a break from previous comments saying he would like to see restrictions eased by Easter.

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The change of heart, Fauci said, came when he and Birx presented the President with data showing new estimates that between 100,000 and 200,000 Americans could die from the virus. “He looked at the data and he got it right away,” Fauci said. “He shook his head and said ‘I guess we’ve got to do it.’”

Trump sees his first goal, Fauci told CNN, as being to “prevent suffering and death.” Fauci and Birx, Fauci said, “made it very clear to him that if we pulled back on what we were doing, and didn’t extend [the current measures], there would be more avoidable suffering and avoidable death. So it was a pretty clear decision on his part.”

But Fauci said he would “not be surprised if we saw 100,000 deaths,” adding that the U.S. could still see a death toll of up to 200,000 even if the new measures were followed closely. “If you look at seasonal flu, we had a bad season in 2017-18,” Fauci said. “We lost over 60,000 people, just in a seasonal flu. This is clearly worse than that.”

There was an economic argument too, Fauci suggested, for continuing to push social isolation in the face of COVID-19. “It was patently obvious, looking at the data, that at the end of the day, if we tried to push back prematurely, not only would we lose lives but it probably would even hurt the economy,” he said.

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Write to Billy Perrigo at billy.perrigo@time.com.