WASHINGTON (REUTERS) - President Joe Biden on Thursday (Sept 9) took aim at vaccine resistance in America, announcing policies requiring most federal employees to get Covid-19 vaccines and pushing large employers to have their workers vaccinated or tested weekly.

The new measures, which Biden laid out in remarks from the White House, would apply to about two-thirds of all US employees, those who work for businesses with more than 100 workers.

"We've been patient," Biden told the millions of Americans who have declined to get coronavirus shots. "But our patience is wearing thin, and your refusal has cost all of us."

Taken together, the policies and speech represented Biden's most aggressive steps yet to prod Americans resistant to getting shots as the fast-spreading Delta variant sparks a new wave of sickness and death.

The surge has posed increased risk not just to the country but also to a president who ran on promises to get control of the pandemic.

Biden's approval ratings have sagged since he said in July the United States was "closer than ever to declaring our independence from a deadly virus."

Biden's latest moves are expected to be the subject of political and legal challenges.

Despite a full-throttle campaign by the Biden administration urging all eligible Americans to get the free vaccines, just over 62 per cent of eligible Americans are fully vaccinated, according to data from the US Centres for Disease Control and Prevention (CDC).

On Thursday, Biden warned that "we're in a tough stretch and it could last for a while."

Infectious disease and health policy experts said the mandates are unlikely to significantly change infection rates quickly.

Still, they would help against potential future waves of the virus, reducing deaths and hospitalisations and alleviating the stress on the healthcare system, said Georgetown University's Dr Jesse Goodman, a former chief scientist at the US Food and Drug Administration.

"It's absolutely the right thing to do," he said. "Ideally everyone would have been vaccinated already."

In a televised speech running a bit under half an hour, the Democratic president accused "a distinct minority of elected officials" who have resisted mask and vaccine mandates on freedom-of-choice and economic grounds as "making people sick."

The White House Covid-19 recovery plan was based on the vast majority of eligible Americans being vaccinated this year.

But the public health issue has become politicised, with a vocal minority refusing the shots and mask mandates.

Florida Republican Governor Ron DeSantis issued an executive order in July blocking mask mandates in schools.

Administration medical officials have said over 97 per cent of people hospitalised with Covid-19 are not vaccinated, and those people account for an even higher share of deaths.

Cathy McMorris Rodgers, the senior Republican on the House of Representatives committee that oversees health policy, said Biden "is using fear, control, and mandates."

The Republican National Committee said it intends to sue the Biden administration over the vaccine mandate.

Under Biden's plan, the administration will also require vaccinations for more than 17 million healthcare workers at hospitals and other institutions that participate in Medicare and Medicaid social programmes for poor, disabled and older Americans, senior administration officials said.

Biden previously required that federal employees be vaccinated or get tested. Now federal workers have 75 days to get vaccinated, or face termination unless they fall into limited exemption categories.

Federal workers unions suggested on Thursday they would accept the vaccine mandate.

Substantial fines

The US Labour Department's Occupational Safety and Health Administration (OSHA) will issue its rule for private companies to require vaccines or tests in coming weeks. OSHA plans to take enforcement actions against those that did not comply, with substantial fines of nearly US$14,000 (S$18,000) per violation.

The administration is also calling on entertainment venues to require tests or shots and for states to adopt mandates for school employees.

It is also multiplying the fines charged to people who fail to wear masks on airplanes, trains and buses.

The administration also plans to ramp up testing capacity for the virus.

Biden will use his authority under the Defence Production Act to spur industry to accelerate production of the tests, and big retailers including Walmart, Amazon.com and Kroger are expected to sell the tests at cost for the next three months to make them more affordable.

Critics have said the Biden administration has not done enough on testing during its seven months in office.

Still, the new demand for tests could tax already strained suppliers.

The full recovery of the US economy depends on blunting the spread of the virus, which is a key health and political goal of the president, who entered the White House in January.

Administration officials believe the full recovery of the US economy depends on blunting the spread of the virus, the key focus of the president since entering office in January.

More than 654,000 deaths

The disease has killed more than 654,000 people in the United States, and deaths and hospitalisations have been rising sharply as the easily transmissible Delta variant of the virus spreads.

The spread of the Delta variant has raised concerns as children head back to school, while also rattling investors, upending company return-to-office plans, and tamping down hiring.

The White House plans to offer booster shots providing additional protection to those who are fully vaccinated.

But supplies are limited and the World Health Organisation has begged rich countries pause booster programmes until more people worldwide are inoculated.

But with Delta causing more symptomatic breakthrough infections among fully inoculated individuals, most vaccinated Americans want a booster, a recent Reuters/Ipsos opinion poll found. Boosters could begin the week of Sept 20.

"Get vaccinated," Biden urged in closing his speech.