WASHINGTON, D.C. — President Trump on Sunday sharply revised upward his projected toll of U.S. coronavirus deaths, saying that fatalities could reach 100,000, even as he defied warnings from leading public health experts and renewed his calls for a quick reopening of businesses across the country.

Speaking at a Fox News event staged at the Lincoln Memorial, Trump acknowledged being warned in late January about the threat posed by the virus, but faulted officials who he said delivered their assessment “matter-of-factly — it was not a big deal.”

Earlier Sunday, health experts from inside and outside the government warned the outbreak may flare up more fiercely in the coming months, even as many U.S. states are moving to ease stay-at-home restrictions.

Several of the nation’s governors, meanwhile, acknowledged they were walking a tightrope, fearing intensified outbreaks even as some of them embarked on reopenings meant to ease deep economic distress in their states.

As the U.S. death toll rose, White House coronavirus coordinator Dr. Deborah Birx implicitly acknowledged that Trump, as recently as last month, had been overly optimistic about likely fatalities.

In an interview on “Fox News Sunday,” Birx said the administration continued to operate on the assumption that the more likely scenario called for as many as nearly a quarter-million deaths — even with shutdown measures taken to date.

“Our projections have always been between 100,000 and 240,000 American lives lost,” she said. “And that’s with full mitigation, and us learning from each other how to social distance.”

As he has done during weeks of White House briefings on the virus and efforts to fight it, Trump used his forum on Fox to tout his own response to the coronavirus crisis and to rail against Democrats, his predecessor, selected governors, the news media and China, where the virus originated.

Only two weeks ago, Trump was predicting 50,000 or 60,000 Americans might die. But Sunday, with the toll surpassing 66,000, he acknowledged the parameters had changed.

“We’re going to lose anywhere from 75, 80 to 100,000 people,” he said, calling that scenario “horrible.”

As he has from early in the outbreak, the president again called for a reopening of business, coupling that with a prediction that the economy would rebound this summer and boom next year — if he is reelected.

“We have to get our life back,” he said. “We have to get the country back.”

But many experts counseled caution earlier Sunday.

Scott Gottlieb, the former commissioner of the Food and Drug Administration, said on CBS’s “Face the Nation” that there were rising numbers of new cases in about 20 states, suggesting that the outbreak was not yet being tamped down to the degree that officials had hoped.

“While mitigation didn’t fail, I think it’s fair to say that it didn’t work as well as we expected,” he said. “We expected that we would start seeing more significant declines in new cases and deaths around the nation at this point. And we’re just not seeing that.”

Looking ahead to the fall, Gottlieb said that by autumn, after a summer break, “you can see this slow simmer explode into a new epidemic or large outbreaks.

“That’s the concern — that if we don’t snuff this out more, and you have this slow burn of infection, it can ignite at any time,” he said.

Another leading expert, Thomas Inglesby, director of the Center for Health Security at Johns Hopkins University, said that “overall, as a country, we still have a long way to go.”

Inglesby said on NBC’s “Meet the Press” that in the autumn, the limits of the nation’s healthcare system will be tested by seasonal influenza as well as the continuing presence of COVID-19, the disease caused by the coronavirus.

“COVID[-19] will be mixed with flu, and will both be contributing to hospitalizations and [intensive-care] beds,” he said, predicting “two concurrent large public health challenges at the same time.”

Reopenings are beginning in many parts of the country even though, as of Sunday, no state had met federal guidelines calling on states to wait for a 14-day period of continually declining cases.

Mississippi, for example, is pressing ahead with an easing of restrictions even though its number of confirmed cases just jumped. Gov. Tate Reeves, a Republican, said the increase reported Friday, the biggest single-day increase to date, was a “one-day blip.”

“You have to understand that Mississippi is different than New York and New Jersey,” Reeves said on “Fox News Sunday,” adding that “sometimes the models are just different for different states.”

In recent weeks, Trump has frequently singled out individual states or governors for criticism over stay-at-home policies. He did so again Sunday, tweeting that “many complaints” were coming in about Maine’s stay-at-home orders.

“Don’t make the cure worse than the problem itself,” he wrote on Twitter, citing the case of a Maine brewpub that lost its state health and liquor licenses after reopening its doors in defiance of state rules.

Birx, in her earlier Fox interview Sunday, said the sight of anti-shutdown protesters crowded together in public, often unmasked, is deeply concerning.

“It’s devastatingly worrisome to me personally,” she said, “because if they go home and they infect their grandmother or grandfather who has a comorbid condition and they have a serious or very unfortunate outcome, they will feel guilty for the rest of their lives.”

As infections have progressed, many governors have sought to avoid direct criticism of Trump for fear of endangering access to supplies and other federal aid. But some state chief executives who have repeatedly drawn his disfavor offered veiled but unmistakable criticism of his rhetoric and performance Sunday.

Michigan Gov. Gretchen Whitmer, who was urged by Trump last week to “make a deal” with armed anti-shutdown demonstrators who entered the state Capitol, said governors should act in accordance with public health imperatives, however painful.

“This isn’t something we just negotiate ourselves out of,” she said on CNN’s “State of the Union.”

Trump has defended the gun-toting protesters in Michigan as “very good people,” and Whitmer, who has been touted as a potential running mate for Joe Biden, agreed in the CNN interview that demonstrators have a right to voice their views.

But she decried the display of emblems such as “Confederate flags and nooses,” saying they symbolize “some of the worst racism” in U.S. history.

Illinois Gov. J.B. Pritzker, another Democrat, contested the assertion last week by Jared Kushner, a senior White House aide and Trump’s son-in-law, that the federal government had risen to the challenge of dealing with the pandemic.

“It’s the governors that have risen to the challenge,” Pritzker said on CBS’ “Face the Nation,” adding that “much of what came out of the White House for many weeks was not helpful.”

Also Sunday, Trump lashed out at former President George W. Bush, a day after Bush issued a message calling for national unity amid the coronavirus crisis. In a tweet Sunday morning, Trump said Bush, a fellow Republican, should have voiced support for him when the House impeached the president late last year.

“He was nowhere to be found in speaking up against the greatest Hoax in American history!” Trump wrote of Bush, after citing similar comments from a Fox News anchor.

Throughout the coronavirus outbreak, Trump has often used Twitter and White House briefings on the virus to excoriate political foes. Sometimes he responds to the perceived denigration of his pandemic response, but sometimes he brings up grudges and grievances unrelated to the crisis.

Bush’s three-minute video, shared Saturday on Twitter, called on all Americans to remember “how small our differences are” in the face of the pandemic.

“In the final analysis, we are not partisan combatants, we are human beings, equally vulnerable and equally wonderful in the sight of God,” the former president said. “We rise or fall together, and we are determined to rise.”