WASHINGTON — President Joe Biden on Thursday is announcing sweeping new federal vaccine requirements affecting as many as 100 million Americans in an all-out effort to increase COVID-19 vaccinations and curb the surging delta variant that is killing thousands each week and jeopardizing the nation’s economic recovery.

The expansive rules mandate that all employers with more than 100 workers require them to be vaccinated or test for the virus weekly, affecting about 80 million Americans. And the roughly 17 million workers at health facilities that receive federal Medicare or Medicaid also will have to be fully vaccinated.

Biden is also signing an executive order to require vaccination for employees of the executive branch and contractors who do business with the federal government — with no option to test out. That covers several million more workers.

Biden was to announce the new requirements in a Thursday afternoon address from the White House as part of a new “action plan” to address the latest rise in coronavirus cases and the stagnating pace of COVID-19 shots that has raised doubts among the public over his handling of the pandemic.

Just two months ago Biden prematurely declared the nation’s “independence” from the virus. Now, despite more than 208 million Americans having at least one dose of the vaccines, the U.S. is seeing about 300% more new COVID-19 infections a day, about two-and-a-half times more hospitalizations, and nearly twice the number of deaths compared to the same time last year.

Biden’s plans were previewed Thursday afternoon by White House press secretary Jen Psaki and other senior administration officials ahead of the speech.

After months of using promotions to drive the vaccination rate, Biden is taking a much firmer hand, as his aides blame people who have not yet received shots for the sharp rise in cases that is killing more than 1,000 people per day and imperiling a fragile economic rebound.

Psaki said Biden’s “overarching objective here is to reduce the number of unvaccinated Americans,” noting about 80 million adults remain unvaccinated.

An AP-NORC poll conducted in August found that 54% of Americans approved of Biden’s stewardship of the public health crisis, down from 66% the month before, driven by a drop in support from Republicans and political independents.

In addition to the vaccination requirements, Biden is moving to double federal fines for airline passengers who refuse to wear masks on flights or to maintain face covering requirements on federal property in accordance with Centers for Disease Control and Prevention guidelines.

Biden was also to announce that the federal government will work to increase the supply of virus tests, and that the White House has secured concessions from retailers including Walmart, Amazon, and Kroger to sell at-home testing kits at cost beginning this week.

The administration is also to send additional federal support to assist schools in safely operating, including additional funding for testing. And Biden will call for large entertainment venues and arenas to require vaccinations or proof of a negative test for entry.

The requirement for large companies to mandate vaccinations or weekly testing for employees will be enacted through a forthcoming rule from the Occupational Safety and Health Administration that carries penalties of $14,000 per violation, an administration official said. The White House did not immediately say when it would take effect, but said workers would have sufficient time to get vaccinated.

The rule would also require that large companies provide paid time off for vaccination.

Meanwhile, the Centers for Medicare & Medicaid Services will extend a vaccination requirement issued earlier this summer — for nursing home staff — to other healthcare settings including hospitals, home-health agencies and dialysis centers.

Separately, the Department of Health and Human Services will require vaccinations in Head Start Programs, as well as schools run by the Department of Defense and Bureau of Indian Education, affecting about 300,000 employees.

Biden’s order for executive branch workers and contractors includes exceptions for workers seeking religious or medical exemptions from vaccination, according to Psaki. Federal workers and contractors will have 75 days to get fully vaccinated. Workers who don’t comply will be referred to their agencies’ human resources departments for counseling and discipline, to include potential termination.

“We would like to be a model” to other organizations and business around country, Psaki said of the federal workforce. The AP-NORC poll found 55% of Americans in favor of requiring government workers to be fully vaccinated, compared with 21% opposed.

Biden has encouraged COVID-19 vaccine requirements in settings like schools, workplaces and university campuses, and the White House hopes the strengthened federal mandate will inspire more businesses to follow suit. On Thursday, the Los Angeles Board of Education was expected to vote on requiring all students 12 and older to be fully vaccinated in the the nation’s second-largest school district.

The Department of Veterans Affairs, Department of Health and Human Services, the Indian Health Service, and the National Institutes of Health have previously announced vaccine requirements for much of their staffs, and the Pentagon moved last month to require all servicemembers to get vaccinated. Combined, the White House estimates those requirements cover 2.5 million Americans. Thursday’s order is expected to impact nearly 2 million more federal workers and potentially millions of contractors.

More than 177 million are fully vaccinated against the coronavirus, but confirmed cases of the virus have shot up in recent weeks to an average of about 140,000 per day with on average about 1,000 Americans dying from the virus daily, according to data from the Centers for Disease Control and Prevention.

Most of the spread — and the vast majority of severe illness and death — is occurring among those not yet fully vaccinated against the virus. So-called breakthrough infections in vaccinated people occur, but tend to be far less dangerous.

“We cannot accept this to be the new normal,” said Dr. Leana Wen, a former Baltimore health commissioner who comments regularly on the pandemic.. If the pandemic continues unabated, it will mean 500,000 deaths a year. “Surely no one wants that.”

Wen has been urging the White House to take a stronger line on vaccine requirements, including the use of so-called vaccine “passports” for travel and workplace mandates that leave little wiggle room.

“I want to see the full power of the federal government here, and not more half measures,” she said. “I want to see a hard reset from the Biden administration, not more nibbling around the edges.”

Federal officials are moving ahead with plans to begin administering booster shots of the mRNA vaccines to bolster protection against the more transmissible delta variant of the virus. Last month Biden announced plans to make them available beginning on Sept. 20, but only the Pfizer vaccine will likely have received regulatory approval for a third dose by that time. Federal regulators are seeking additional data from Moderna that will likely delay its booster approval until October.

Officials are aiming to administer the booster shots about eight months after the second dose of the two-dose vaccines.