Biden announces federal workers must be vaccinated or face regular tests.

President Biden on Thursday announced that all civilian federal employees must be vaccinated against the coronavirus or be forced to submit to regular testing, social distancing, mask requirements and restrictions on most travel.

“We all want our lives to get back to normal, and fully vaccinated workplaces will make that happen more quickly and more successfully,” Mr. Biden said, speaking in the East Room. “We all know that in our gut. With incentives and mandates, we can make a huge difference and save a lot of lives.”

The federal government employs more than 4 million Americans, all of whom will need to attest to being fully vaccinated in order to avoid wearing a mask on the job, regardless of where in the country they work, and comply with screening tests once or twice a week.

The president also directed the Defense Department to study how and when to add the coronavirus vaccine to the list of required vaccinations for all members of the military. The announcement marked the first time he has suggested that a mandate could come for active-duty members of the military before any of the three federally authorized vaccines receives full approval from the Food and Drug Administration.

Mr. Biden’s announcement of new mandates in a pleading speech was part of an attempt to reset expectations on the health scourge that just weeks ago he thought he had under control. On July 4, the White House celebrated the national holiday as a day of “independence from Covid-19.”

But now, the Delta variant is ripping through unvaccinated communities, threatening to undo the progress to stop the spread of the coronavirus made by the Biden administration in its first six months. Recent research has shown fully vaccinated people are protected against the worst outcomes of Covid-19, including those involving the Delta variant. And cases, hospitalizations and deaths are still a fraction of their devastating winter peaks.

“Cases will go up further before they start to go back down,” Mr. Biden said Thursday, tempering expectations for what is to come. “There’s a challenge as you knew there could be.”Mr. Biden acknowledged the news was frustrating. “I know we hoped this would be a simple straightforward line without problems or new challenges, but that isn’t real life,” he said.

For vaccinated Americans worried about breakthrough cases, Mr. Biden reiterated that the pandemic was among the unvaccinated and that booster shots were not necessary. The Centers for Disease Control and Prevention has been tracking breakthrough infections that result in hospitalization and death and the director said this week the agency is conducting outbreak investigations in clusters.

“As of now, my medical advisers say the answer is no,” he said of booster shots. “No American needs a booster now. But if science tells us there’s a need for boosters, that’s something we’ll do.”

In response, the administration is stepping up its efforts to convince unvaccinated Americans to get their shots. Mr. Biden on Thursday called on states, territories and local governments to pay $100 to Americans who remain unvaccinated to get their shots. And the administration announced Thursday that small- and medium-sized businesses will now be reimbursed for offering their employees paid leave to get their family members, including their children, vaccinated.

“It will cost you, the employer, nothing,” he said.

Some experts, especially in the early days of the vaccination campaign, have expressed concern over the idea of paying people to get vaccinated, worrying that it could be perceived as out of step with messaging that vaccines bring enormous benefits on their own.

Mr. Biden also called on school districts across the country to host at least one pop-up vaccination clinic over the coming weeks, with the goal of increasing vaccination rates among children 12 and older.

Other governments around the country are beginning to put in place similar arrangements as well, as the highly contagious Delta variant has caused case numbers to balloon in recent weeks. New York City will require all 300,000 city employees to be vaccinated or submit to weekly testing, and New York State will require tens of thousands of state employees to show proof of vaccination or submit to weekly testing and will mandate patient-facing health care workers at state-run hospitals to be vaccinated as a condition of their employment. California also unveiled a plan to require vaccinations for state employees.

The North Carolina Department of Health and Human Services will require all workers and volunteers at state-operated facilities to be fully vaccinated or receive an approved medical or religious exemption by Sept. 30, according to a statement sent to The New York Times on Wednesday. Officials had not responded to questions about whether those with exemptions will be required to undergo testing.

And the Department of Veterans Affairs will require 115,000 of its frontline health care workers to be vaccinated against the coronavirus in the next two months. But public health officials are hoping that the prospect of extra burdens for the unvaccinated will help persuade more people to get inoculated.

People familiar with Mr. Biden’s announcement said it was part of a longstanding discussion about how to bring most federal workers back to the office after nearly a year and a half in which hundreds of thousands of them worked from home because of the pandemic.

A team has been working on that plan for months, trying to juggle the concerns of employees and the need to keep the government functioning. One concern that officials confronted was how to require vaccinations without potentially prompting critical employees to quit, undermining the government’s mission.

But the president’s announcement comes as the administration is under pressure to increase the rate of vaccinations in the country. About half of all Americans have been fully vaccinated, but the pace of vaccinations has declined significantly from early spring.

On Tuesday, the C.D.C. revised its mask guidance, advising that even vaccinated people should resume wearing masks in public indoor spaces in parts of the country where the virus is surging. Some states and municipalities were quick to update their own mask rules, while others expressed outrage. Mayor Muriel Bowser of Washington, D.C., said Thursday that an indoor mask mandate would be reimposed on Saturday to comply with new federal guidance.

Rebecca Robbins and Dan Levin contributed reporting.