The president announced the purchase of another 500 million tests, doubling the number ordered last month, to be distributed free to Americans.
Limited availability is the latest issue in nearly two-year saga of stumbles on coronavirus testing in the U.S.
A $70 million effort will help manufacturers produce the data needed as part of the regulatory process.
GOP leaders argue that vaccine requirements violate personal freedoms, but experts say mass vaccinations have not worked historically without mandates.
A Washington Post survey of the 20 largest school districts found that few are offering robust coronavirus testing amid vague guidelines and a surge of cases that few anticipated.