WASHINGTON (AP) — President Donald Trump is set to deliver his first public remarks Friday since his defeat by President-elect Joe Biden, as he seeks to highlight positive developments in the race for a vaccine for the resurgent coronavirus, even as he refuses to concede the election.

Trump is set to speak in the Rose Garden as the nation sets records for confirmed cases of COVID-19, hospitalizations near critical levels and fatalities climb to the highest levels since the spring.

Public health experts worry that Trump's refusal to take aggressive action on the pandemic or to coordinate with the Biden team during the final two months of his presidency will only worsen the effects of the virus and hinder the nation's ability to swiftly distribute a vaccine next year.

And as cases reach new heights, Trump's campaign prediction that the U.S. was "rounding the turn" on the pandemic has met a harsh reality, with his own White House becoming the focus of yet another outbreak.

Trump's aggressive travel despite the virus has taken its toll on his protectors as well. The U.S. Secret Service is experiencing a significant number of cases, many believed to be linked to his rallies in the closing days of the campaign, according to one official.

White House press secretary Kayleigh McEnany, meanwhile, said Trump is "not even at that point yet" when it comes to conceding to Biden. Trump has leveled baseless allegations of widespread voter fraud, even as his own administration has said there is no evidence to support the claims. His aides suggest he is merely trying to keep his base of supporters on his side in defeat.

Trump spoke with conservative media on Friday, including Fox News' Geraldo Rivera, suggesting he would acknowledge the loss only after exhausting his legal options.

"You know, he told me he was a realist," Rivera said. "He told me he would do the right thing."

With more than 100,000 new confirmed U.S. cases reported daily for more than a week, Trump has been more focused on tracking the rollout of a vaccine, which won't be widely available for months. He has fumed that Pfizer intentionally withheld an announcement about progress on its vaccine trial until after Election Day, according to a White House official who was not authorized to publicly comment and spoke on condition of anonymity. Pfizer said it did not purposely withhold trial results.

Although the president has consistently played down the pandemic, which has killed more than 240,000 Americans and infected more than 10 million people in the U.S., public health experts expressed worry about Trump's silence on the troubling spike in cases, as well as his refusal to begin coordination on virus issues with Biden's transition team.

"It's a big problem," said Dr. Abraar Karan, a global health specialist at Brigham and Women's Hospital and Harvard Medical School. "The transition is not going to happen until January, and we are in a complete crisis right now. We already know where this is headed. ... It's not good enough to say we're going to wait until the next president to address this."

Trump hasn't answered questions since before Election Day. That hasn't slowed his Twitter habit, but he's used it almost exclusively in recent days to rage over the election results and spread unsubstantiated allegations of voter fraud.

By late Thursday afternoon, Trump had tweeted or retweeted more than three dozen times that day. Just one was related to the virus — a retweet of a posting by Sen. David Perdue about Georgia receiving 2,000 vials of a new antibody treatment.

White House chief of staff Mark Meadows tested positive last week after attending an election night party at the White House. Others at the party also have tested positive, including White House political director Brian Jack, former White House aide Healy Baumgardner and Trump campaign advisers David Bossie and Corey Lewandowski. Lewandowski said Thursday that he believes he contracted the virus in Philadelphia while assisting the president's election challenge there.

Biden, for his part, largely framed the election as a referendum on Trump's handling of the pandemic. He has made addressing the virus his top priority as he moves forward with his transition. He spoke by phone Thursday with House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer about the intensifying pandemic and prospects for passage of a COVID-19 relief bill in the lame duck session of Congress.

Incoming White House chief of staff Ron Klain said Biden will appoint a "COVID coordinator" who will lead the administration's pandemic response. Klain, speaking on MSNBC Thursday night, said the individual will have "direct access" to the president and will brief him daily on the pandemic. A team of people underneath the coordinator will supervise vaccine distribution, address supply chain disruptions and improve access to testing.

Lawrence Gostin, a public health expert at Georgetown University's law school, said Biden will only be able to "scratch the surface" of tackling a pandemic that could be a "raging forest fire" by the time he takes office on Jan. 20.

He added that even the good news on Pfizer's development of a vaccine that showed 90% efficacy in early trial results could be diminished if Trump doesn't begin coordination efforts with Biden's team on how to roll out the vaccine. Some public health experts believe the task of persuading Americans to take the vaccine and widely distributing it could be as complicated as the vaccine's development.

"I fear the next three months ahead could be the worst we've faced during the pandemic," Gostin said. "America is like a ship at storm, and the captain has decided to go play golf."

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Madhani reported from Chicago. Associated Press writers Jill Colvin and Alexandra Jaffe contributed to this report.