The Biden administration, looking ahead to a possible winter surge of Covid-19, announced on Wednesday that it was reviving its program of offering Americans free coronavirus tests through the mail and would spend $600 million to buy tests from a dozen domestic manufacturers.

The website for the program, covidtests.gov, will begin accepting orders on Monday, and households will receive four tests. Dawn O’Connell, the assistant secretary for preparedness and response at the Department of Health and Human Services, said the money would fund the purchase of 200 million tests to replenish the nation’s stockpile as tests are sent out.

But a byproduct of the program, Ms. O’Connell said, is that it will shore up domestic manufacturing capacity in the event of another serious coronavirus surge. And if there is a spike in demand, she said, the department has given the manufacturers permission to sell the tests directly to retailers ahead of the government.

Coronavirus hospitalizations have been on the rise in the United States, though they remain low compared with earlier stretches of the pandemic, and free tests are now harder to come by for many Americans. While private insurers had previously been required to cover up to eight at-home tests per month, that requirement ended when the Biden administration allowed the public health emergency for the coronavirus to expire in May.

The administration first began offering free at-home coronavirus tests through the Postal Service early last year after the Omicron variant caused cases to soar. More than 600 million tests were distributed before officials halted the program late that summer, citing a lack of funding. The administration then resumed offering tests late last year before halting the program again this spring.

The announcement on Wednesday came as President Biden’s health secretary, Xavier Becerra, tried to drum up interest in the newly approved coronavirus vaccines by getting his own Covid and flu shots at a CVS pharmacy in Washington. The Centers for Disease Control and Prevention recommended last week that all Americans 6 months and older receive at least one dose of the reformulated Covid vaccines from Pfizer-BioNTech and Moderna.

With the chief executives of Pfizer and Moderna standing beside him, Mr. Becerra invoked his own mother, who is about to turn 90 and, he said, has not had Covid-19.

“I feel comfortable, having gotten the shots, that I could hug and kiss my mother and not be responsible for getting her sick,” he said, adding, “No one is safe until everyone is safe.”