US President Joe Biden is testing tougher approaches to tackle the COVID-19 pandemic in the country after testing waters with incentives like million-dollar cash lotteries when the pace of vaccinations in the US first began to slow.

In just the past two weeks, Biden has forced millions of federal workers to attest to their vaccination status or face new testing requirements. He has met with business leaders at the White House to press them to do the same, according to Associated Press inputs.

Meanwhile, the administration has taken steps toward mandating vaccines for people traveling into the US from other countries. And the White House is weighing options to be more assertive at the state and local level, including potential support for school districts imposing rules to prevent the spread of the virus even as Republican leaders continue to object.

“To the mayors, school superintendents, educators, local leaders, who are standing up to the governors politicizing mask protection for our kids: thank you. Thank God that we have heroes like you, and I stand with you all, and America should as well,” Biden was quoted by Associated Press on Thursday.

But even as Biden becomes more aggressive, he has refrained from using all of his powers to pressure Americans to get vaccinated. He is holding off on proposals to require vaccinations for all air travelers and the federal workforce. 

Vaccine mandates are “the right lever at the right time,” AP quoted Ben Wakana, the deputy director of strategic communications and engagement for the White House COVID-19 response as saying. He noted that the public’s confidence in the vaccines is increasing that it marks a new phase in the government’s campaign to encourage Americans to get shots.

Many Republicans, particularly those eyeing the party’s 2024 presidential nomination, disagree and warn of federal overreaching into decisions that should be left to individuals. Biden and Governor Ron DeSantis of Florida, an epicenter of the latest virus wave, have spent weeks feuding over the proper role of government during a public health crisis.

There is notable support for vaccine mandates in the country. According to a recent poll from the Kaiser Family Foundation, 51% of Americans say the federal government should recommend that employers require their workers to get vaccinated, while 45% say it should not.

For now, Biden has required most federal workers to attest to their vaccination status under potential criminal penalties, with those who have not received a dose required to social-distance, test weekly for the virus, and face other potential restrictions on their work.

Health workers at the Department of Veterans Affairs and the Department of Health and Human Services will be required to get vaccinated, and the Pentagon’s announced that it intends to mandate vaccines for the military by next month.

The sharper federal approach comes as nearly 90 million eligible Americans still have not been vaccinated and as Dr Anthony Fauci, the nation’s top infectious disease expert, says shots are the only path for the nation to contain the Delta variant.