WASHINGTON — Fighting the omicron variant surging through the country, President Joe Biden announced the government will provide 500 million free rapid home-testing kits, increase support for hospitals under strain and redouble vaccination and boosting efforts.

At the White House on Tuesday, Biden detailed major changes to his COVID-19 winter plan, his hand forced by the fast-spreading variant, whose properties are not yet fully understood by scientists. Yet his message was clear that the winter holidays could be close to normal for the vaccinated while potentially dangerous for the unvaccinated.

His pleas are not political, he emphasized. He noted that former President Donald Trump has gotten his booster shot, and he said it’s Americans’ “patriotic duty” to get vaccinated.

“It’s the only responsible thing to do,” the president said. “Omicron is serious and potentially deadly business for unvaccinated people.”

Biden chastised social media and people on cable TV who have made misleading statements to discourage people from getting vaccinated.

The outbreak from this latest strain of the coronavirus has required the federal government to get more aggressive in addressing the wave of infections, but Biden promised a weary nation that there would not be a mass lockdown of schools or businesses.

“I know you’re tired, and I know you’re frustrated. We all want this to be over. But we’re still in it,” Biden said. “We also have more tools than we had before. We’re ready, we’ll get through this.”

Scientists don’t know everything about omicron yet, but they do know that vaccination should offer strong protection against severe illness and death.

The variant has spread at such an alarming rate since it was identified in South Africa about a month ago that the Biden administration snapped into action to offer new tests and additional aid. Still more is needed, some medical experts said.

A cornerstone of the plan is for the government to purchase 500 million coronavirus rapid tests for free shipment to Americans starting in January. People will use a new website to order their tests, which will then be sent by U.S. mail at no charge. The 500 million could be increased, depending on developments.

It marks a major shift for Biden, who earlier had called for many Americans to purchase the hard-to-find tests on their own and then seek reimbursement from health insurance. For the first time, the U.S. government will send free COVID-19 tests directly to Americans, after more than a year of urging by public health experts.

Experts had criticized Biden’s initial buy-first, get-paid-later approach as unwieldy and warned that the U.S. would face another round of testing problems at a critical time. Testing advocates point to nations including the U.K. and Germany, which have distributed billions of tests to the public and recommend people test themselves twice a week.

The federal government will also establish new testing sites and use the Defense Production Act to help manufacture more tests. The first new federally supported testing site will open in New York this week. The new sites will add to 20,000 already available. White House officials said they’re working with Google so that people will be able to find them by searching “free COVID test near me.”

Still, Biden’s testing surge would need to be supported by a further jump in production for all Americans to test at the recommended rate of twice weekly. The U.S. would need 2.3 billion tests per month for everyone 12 and older to do that, according to the nonprofit Kaiser Family Foundation. That’s nearly five times the half-billion tests Biden will deploy.

Currently, the U.S. can conduct about 600 million tests per month, with home tests accounting for about half, according to researchers from Arizona State University.