For a moment Friday, President Trump seemed to acknowledge — however fleetingly — the reality of his electoral defeat.

Offering an update on coronavirus vaccine progress from the Rose Garden late Friday afternoon, the president first asserted that “this administration will not be going to a lockdown.”

But then he faltered.

“Hopefully the — the,” Trump said, seeming poised to blurt out what has long been unthinkable to him: the Biden administration.

“Whatever happens in the future,” he continued, muscling ahead. “Who knows, which administration it will be — I guess time will tell — but I can tell you this administration will not go to a lockdown.”

Those 20 halting words in the middle belied Trump’s outward confidence and baseless claims that he can still win the 2020 presidential election after all, despite President-elect Joe Biden projected to have 306 electoral votes to his 232 votes.

“Lockdowns cost lives, and they cost a lot of problems,” Trump said, before ticking through consequences including drug and alcohol abuse, depression, economic calamity. “It’s a terrible thing. So, this administration will not go under any circumstances, will not go to a lockdown, but will be very vigilant, very careful.”

Friday’s news conference marked Trump’s first public comments after a full week of near-hibernation — and the first faint public hint that he understands his time in the White House is waning.

Privately, Trump has matter-of-factly discussed a 2024 presidential run — something that would be unconstitutional were he expecting to serve a second consecutive term right now. And his firing by tweet on Monday of Defense Secretary Mark T. Esper was viewed by many allies as the opening salvo of a broader purge of his national security and defense apparatus — part grudge-settling and part installing loyalists to aid him with some final unidentified goals.

After pharmaceutical behemoth Pfizer announced Monday that it had developed a coronavirus vaccine that was more than 90 percent effective, Trump’s advisers had been urging him to tout the apparent success, which they argued was one of the key achievements of his presidency. But the president was reluctant to do so, angry that Pfizer had waited until after the election to announce the encouraging news — and believing that the drug company and his own Food and Drug Administration had withheld news that could have helped him at the polls.

Friday’s Rose Garden announcement, then, was that delayed victory lap — but Trump displayed almost no joy in what could have been a triumphant moment.

Moncef Slaoui, the scientific head of Operation Warp Speed, the effort to spur development of a vaccine, said he expected to have 20 million doses ready for public distribution by December with “another 25 [million] to 30 million per month on an ongoing basis.”

But while the vaccine progress was encouraging for the nation, it was not necessarily good for Trump personally, or at least not for his 2020 prospects against Biden — the only metric he much cares about these days.

And so as Trump rolled out pronouncements — that Operation Warp Speed was “unequaled and unrivaled,” and that it was “five times faster than the fastest vaccine development in history” — he did so with the dour, slightly defeated air of a man who knows his time is coming to an end.

While Vice President Pence several times directly addressed the extent of the raging pandemic — which so far has killed more than 242,000 Americans and sickened millions more — Trump said nothing about those details.

Typical of Trump, he also used the occasion to settle scores with those he felt had aggrieved him.

He took aim at Pfizer itself, apparently still angry that the company had pointedly distanced itself from Operation Warp Speed when, after its vaccine announcement Monday, the Trump administration tried to claim credit.

“Pfizer said it wasn’t part of Warp Speed, but that turned out to be an unfortunate misrepresentation,” Trump said. “And it was an unfortunate mistake that they made when they said that.”

In fact, Pfizer did not accept federal funds for research into its coronavirus vaccine — but it did reach a deal with the administration to sell at least 100 million doses of its vaccine to the government.

At another point, Trump also took aim at New York Gov. Andrew M. Cuomo, a Democrat, who previously said that he did not trust the safety of any vaccine produced under the Trump administration and that he would independently review any drug before distributing it to New Yorkers.

“He doesn’t trust where the vaccine is coming from,” Trump said, referring to Cuomo, with whom he has clashed frequently over the deadly pandemic. “These are coming from the greatest companies anywhere in the world, greatest labs in the world, but he doesn’t trust the fact that it’s this White House, this administration, so we won’t be delivering it to New York until we have authorization to do so, and that pains me to say that.”

Cuomo, Trump added, “will have to let us know when he’s ready for it; otherwise, we can’t be delivering it to a state that won’t be giving it to its people immediately.”

Then, when the news conference was over, Trump — often combative and eager to spar with the White House press corps — turned and sauntered back inside, ignoring shouted questions.