WASHINGTON • President Donald Trump has insisted he would never put the United States into a coronavirus lockdown, but said "time will tell" if another administration takes office in January and does so, the closest he has come to acknowledging that President-elect Joe Biden could succeed him.

In his first public remarks since Mr Biden was widely projected the winner on Nov 7, Mr Trump said he expects a vaccine to be available for the entire population as soon as April, amid a crush of new infections that has pushed daily case counts to record highs.

In broadcast remarks in the White House Rose Garden on Friday, Mr Trump also appeared to acknowledge for the first time the possibility of an upcoming Biden administration, though he stopped short of conceding the race and did not mention his Democratic rival by name.

"Ideally, we won't go to a lockdown. I will not go, this administration will not be going to a lockdown," he said.

"Hopefully, the, the - uh - whatever happens in the future - who knows which administration will be. I guess time will tell."

Since the Nov 3 election, Mr Trump has persisted with unfounded accusations of widespread voting fraud.

But while he has continued to make such claims on Twitter, he did not repeat them in his public remarks on Friday.

At the Rose Garden, the Republican President said he expects an emergency use authorisation for Pfizer's vaccine "extremely soon".

Pfizer has said it expects to report required safety data this week and apply for an emergency use authorisation.

The remarks came after Mr Trump received an update on Operation Warp Speed, an administration effort to turbocharge development of a vaccine.

Criticism of the administration's response to the virus, which has killed more than 244,000 Americans, became a rallying cry for Democrats ahead of the election.

Less than an hour before Mr Trump's address, Mr Biden demanded his predecessor do more to confront the coronavirus infections exploding across the country, calling the federal response "woefully lacking".

In a blistering statement, Mr Biden said the recent surge, which is killing more than 1,000 Americans and hospitalising almost 70,000 every day, required a "robust and immediate federal response".

"I will not be president until next year," Mr Biden said.

"The crisis does not respect dates on the calendar; it is accelerating right now.

"Urgent action is needed today, now, by the current administration - starting with an acknowledgement of how serious the current situation is."

The virus has reportedly even struck the US Secret Service, which guards Mr Trump, Mr Biden and the White House.

The Washington Post said on Friday that more than 130 Secret Service agents were infected by the coronavirus or in quarantine due to contact with infected people.

The outbreak came after numerous agents travelled to campaign rallies with Mr Trump where many officials and most of the attendees did not wear masks.

It also follows several White House events in the past few weeks led by the President, including an election night party on Nov 3, where most of those present also did away with masks.

Afterwards, a number of officials reported positive Covid-19 tests, including Mr Trump's chief of staff Mark Meadows.

Asked about the reports, Secret Service spokesman Julie McMurray said it will not release any details on Covid-19 infections "for privacy and operational security reasons".

Separately, supporters of Mr Trump - who has made little headway in the courts with his lawsuits to overturn Mr Biden's victory - took to the streets yesterday in Washington to back his unsubstantiated claims of election fraud.

Besides in Washington, pro-Trump demonstrations in other cities were also scheduled to feature a mix of the President's backers, far-right personalities and members of the Oath Keepers militia and Proud Boys in a public display of support for his effort to stay in power.

Organisers have given the rallies various names, including the Million Maga March, the March for Trump and Stop the Steal. Maga is an acronym for the Trump campaign slogan Make America Great Again. Mr Trump has tweeted his support.

Some left-wing groups were also planning counter-demonstrations in Washington and other cities.

REUTERS, NYTIMES, AGENCE FRANCE-PRESSE