US President Joe Biden on Thursday took aim at vaccine resistance in America and announced new 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.

"We've been patient, but our patience is wearing thin, and your refusal has cost all of us," Biden said, as quoted by Reuters, in reference to the millions of Americans who have declined to get coronavirus shots.

The new policies represent Biden's most aggressive steps yet to prod Americans resistant to getting shots amid a surge in COVID-19 cases from the fast-spreading Delta variant.

In his remarks, Biden warned that "we're in a tough stretch and it could last for a while."

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 programs for poor, disabled and older Americans, senior administration officials said.

The new vaccination requirements cover about 100 million workers, or about two-thirds of all workers in the United States, officials said, according to Reuters.

Biden previously required 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.

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

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

Biden's plan also calls on large entertainment venues to require vaccination or testing for entry.