Trump slams the F.D.A. ahead of expected vaccine authorization.

President Trump lashed out anew at the Food and Drug Administration in a Friday morning tweet, attacking the agency’s commissioner, Dr. Stephen M. Hahn, by name for not approving a Covid-19 vaccine faster.

Continuing his practice of publicly upbraiding subordinates with whom he is displeased, Mr. Trump told Dr. Hahn to “stop playing games and start saving lives!!!” He called the F.D.A. “a big, old, slow turtle,” flush with funds but mired in bureaucracy.

The F.D.A. has been walking a thin line, trying to fast-track vaccine approval without undercutting public confidence in the process. Dr. Hahn has repeatedly said regulators will not approve a vaccine that has not been proven safe and effective.

The president’s tirade came the morning after an outside advisory panel of experts voted overwhelmingly to recommend that F.D.A. regulators approve a vaccine developed by Pfizer and its German partner, BioNTech, for emergency use.

The regulators are expected to issue the authorization as early as Friday, and in a statement on Friday said it put the Centers for Disease Control and Prevention and those involved with Operation Warp Speed on notice “so they can execute their plans for timely vaccine distribution.”

Mr. Trump has said little about the pandemic in recent weeks, as cases and deaths have been mounting across the country. On Thursday, 2,923 people in the United States died from the virus, according to a Times database. More than 3,000 deaths were reported on Wednesday.

The president has repeatedly accused the F.D.A. and the vaccine-makers themselves of deliberately slowing the approval process in order to harm him politically. Allies of Dr. Hahn have been on tenterhooks for weeks, expecting him to be fired any day.

The president wrote that with “my pushing,” the administration had shaved years off the development of vaccines. “Get the dam vaccines out NOW, Dr. Hahn,” he wrote, misspelling the expletive.

One minute after the president’s tweet posted, Alex M. Azar, the Secretary of Health and Human Services, posted a “BREAKING” message on his official Twitter account, saying the F.D.A. had informed Pfizer that it was moving “rapidly” toward authorizing its vaccine. He was echoing a statement from Dr. Hahn and Dr. Peter Marks, the agency’s top vaccine regulator that officials say was posted before the president’s tweet.

Eileen Sullivan contributed reporting.