The Biden administration’s attempt to compel private companies to require vaccinations or rigorous testing drew stern rebukes from conservatives Friday, split the business community and raised new questions about the federal government’s ability to carry out such a massive mandate.

Republican governors from Texas to Missouri to Georgia have threatened to fight back against the move to force companies with more than 100 employees to require coronavirus vaccinations or regular testing. Texas Gov. Greg Abbott (R) called the mandates “an assault on private businesses” and said the state is “already working to halt this power grab.”

The employer mandates, which the White House estimates could reach as many as 80 million people, or two-thirds of U.S. workers, would be the most extensive government intervention into private companies and employer practices since the pandemic began. The plan, announced Thursday, comes as the highly contagious delta variant of the coronavirus has led to a surge of more than 150,000 new cases a day, mostly among the unvaccinated, while also weighing on the economy.

Companies that ignore the policy could face penalties of up to $14,000 for each violation, according to a senior administration official. Also, companies would be required to give workers paid time off to get vaccinated.

While some companies, such as McDonald’s, Delta Air Lines and Tyson Foods, have already moved to mandate vaccinations or regular testing in their U.S. workforces and offices, the new federal rules threaten to escalate tensions in office workplaces, where some workers have already been arguing about masks and testing rules.

Several larger industry groups said they welcomed the move, in part because it gave some companies more cover for corporate vaccine mandates already in the works.

“America’s business leaders know how critical vaccination and testing are,” which is why many are encouraging customers and employees to get vaccinated and providing paid time off, said Joshua Bolten, president of the Business Roundtable, which represents chief executives from some of the largest U.S. companies, including Chevron, Caterpillar and Citigroup. The group “welcomes the Biden Administration’s continued vigilance in the fight against COVID,” his statement read.

However, the sentiment was not universal. Several local chambers of commerce, as well as the Arizona Small Business Association, declared the move a shock or a federal overreach.

A meatpacking trade group also came out against the vaccine mandates Friday, citing concerns about losing employee, especially amid a worker shortage plaguing large swaths of the nation.

“We believe that the choice to have or not have a vaccine should be the choice of each individual American made in consultation with their family doctor,” said Christopher Young, executive director of the American Association of Meat Processors. “The industry overall will lose good employees who have made the personal decision not to get the vaccine.”

In the meantime, the federal agency tasked with crafting and carrying out the rule, the Occupational Safety and Health Administration, has thus far shied away from requiring stronger workplace safety standards that could help protect workers from getting or spreading the virus. Plus the effort is likely to be challenged in the courts, where the OSHA has had trouble with similar efforts in the past.

The number of promised lawsuits against the White House’s move grew, reflecting conservative anger over the mandates. Wyoming Gov. Mark Gordon (R) said on Twitter that he asked his state’s attorney general “to stand prepared to take all actions to oppose this administration’s unconstitutional overreach of executive power,” and South Dakota Gov. Kristi L. Noem (R) tweeted, “@JoeBiden see you in court.” Georgia Gov. Brian Kemp (R) tweeted that he would “pursue every legal option available to the state of Georgia to stop this blatantly unlawful overreach by the Biden administration.”

Republican National Committee Chairwoman Ronna McDaniel described the new measures as “unconstitutional” and said the group “will sue the administration to protect Americans and their liberties.”

It was not immediately clear how those lawsuits would unfold. “Our lawyers are reviewing President Biden’s plans,” Ian Fury, Noem’s communications director, said in an email to The Washington Post. “The President’s statement yesterday raises serious questions about the legality of his approach. We plan to file our lawsuit when the Biden Administration’s rules or executive orders are finally unveiled and will address the specifics of these unprecedented mandates in our brief to the court.”

Biden on Friday expressed deep frustration and disappointment with Republican governors who he argued have looked to politics more than science when responding to the issue of vaccinations and masks in the country’s schools.

“I am so disappointed that particularly some Republican governors have been so cavalier with the health of these kids, so cavalier with the health of their communities,” he said after touring a D.C. school. “This is what this is. We’re playing for real here. This isn’t a game. And I don’t know of any scientist out there in this field that doesn’t think it makes considerable sense to do the six things I’ve suggested.”

Asked about the GOP countereffort, Biden said Friday, “Have at it.”

Several large companies, including Amazon, praised the White House’s announcement, which included a deal struck with Amazon, Kroger and Walmart to sell at-home coronavirus tests at cost beginning this week. (Amazon founder Jeff Bezos owns The Washington Post.)

“We know vaccines, coupled with widespread and convenient testing, serve as powerful tools to help slow the spread of covid-19 in our communities, keeping the U.S. economy open, and protecting America’s workforce,” Brian Huseman, Amazon vice president of public policy, said in a statement. “We’re proud to work with the Biden administration to increase access to affordable, high-quality, FDA-authorized tests, to keep us moving toward a full recovery.”

One company chief executive said he was relieved to hear about the vaccine mandate, which reinforces what he has been trying to do. Jay Foreman, president and chief executive of Basic Fun, said the toy company already had a policy that resembled the White House’s new rules. Foreman has about 160 employees around the world, roughly 100 of whom are in the United States.

Foreman said he had been hesitant to install a blanket vaccine mandate. So a few weeks ago, the company announced that it would require weekly testing for people who were unvaccinated and that testing would be provided in the office.

An unvaccinated employee was vehemently opposed and “blew a gasket in the office,” Foreman said. The employee acted out to such a degree that he had to be escorted out of the building and was terminated “on the spot,” Foreman said.

The incident did not prompt Foreman to change course. In addition to the testing for unvaccinated employees, people who recently traveled or think they could be at risk also get a weekly test.

“We’re in Florida and continue to be the epicenter,” Foreman said. “All of a sudden everybody knew someone who had covid.”

As some restaurants struggle to hire and retain workers during the pandemic, one major industry group said it supports vaccinations for everyone, encouraging restaurant employees to get the shots. “While we appreciate the intent of this executive order, we hope that the administration will work with us to take into consideration the unique operations of restaurants when creating the guidelines for implementation,” said Sean Kennedy, executive vice president of public affairs for the National Restaurant Association.

Other businesses that had already encouraged employees to get the shots said they would take stock of the new executive order without explicitly endorsing it. “We believe the vaccine plays a critical role in combating the virus and have already designated some roles where we require the vaccine,” Ford Motor Co. said in a statement Friday. “We will be assessing the new executive actions to determine what adjustments need to be made to our current vaccination policy as we continue to prioritize the safety of our employees.”

The National Federation of Independent Business flagged concerns about the rules. In a statement, Kevin Kuhlman, the group’s vice president of federal government relations, said small businesses are already up against daily challenges amid pandemic requirements, a shortage of qualified workers, rising inflation and supply-chain disruptions.

“Small business owners and their employees want to operate in a safe and healthy manner that allows them to stay open,” Kuhlman said. “Additional mandates, enforcement, and penalties will further threaten the fragile small business recovery.”

Other local business groups also said they were worried about the mandate. Rick Murray, chairman of the government affairs committee at the Arizona Small Business Association, said that “this is really as far-reaching as government can get.” He said he was “shocked” that the administration would announce such forceful rules and expected pushback from the organization’s members.

“That’s really a free-enterprise decision that should be made by companies and not the government,” Murray said.

The complicated undertaking comes at a time when the health implications and political stakes of the pandemic have reached a fever pitch, making the proposal arguably the biggest challenge OSHA has faced in its 50-year-history.

“This is certainly the most controversial thing OSHA has ever done,” said Jordan Barab, a workplace safety expert and former OSHA deputy assistant secretary. “It’s very big and very significant.”

Barab said mandatory vaccinations have always been difficult for the agency. For example, the agency did not issue a hepatitis B vaccine mandate for workers who regularly come into contact with blood at work. Instead the agency issued a requirement that companies make the vaccines available to those workers, after much debate, he said. But that pathogen, which is blood-borne, is not easily transmitted between co-workers they way the coronavirus is.

Also, OSHA does not have a great track record in deploying rules in the manner in which the administration is aiming to carry out the vaccine mandate for employers. OSHA would create an emergency temporary standard, a process that allows OSHA to circumvent the months of hearings and testimony needed to implement a new safety rule.

Several previous efforts — to regulate exposure to benzene, a toxic chemical found in plastic, detergents and pesticides, as well as the carcinogen asbestos — failed a short time after being created, after successful challenges in the courts.

Labor experts say this attempt is also nearly certain to be tied up in the legal system.

“An emergency temporary spending is an extraordinarily difficult route to go for OSHA,” said Baruch A. Fellner, an occupational-safety lawyer at the firm Gibson, Dunn and Crutcher. Fellner said that OSHA has even declined to go down the route of attempting to craft an emergency temporary standard, when requested by labor groups, because of its past legal failures.

Labor advocates and workplace safety experts have been clamoring for OSHA to create a standard for workplace safety since the beginning of the pandemic, as outbreaks coursed through workplaces such as meatpacking plants, hospitals, grocery stores, warehouses and prisons. Advocates said they hoped the agency would create a set of unified safety rules that would mandate social distancing, mask-wearing and sanitation procedures to help cut down on these transmissions.

The Trump administration declined to do so. And while Biden directed the agency to study the feasibility of such a standard at the onset of his presidency, his administration shied away from it in the spring as vaccine usage ramped up, and raised hopes that the end of the pandemic was near.

Still advocates were hopeful about the move.

“There are very few federal agencies with the power OSHA has over workplaces, and finally the White House has recognized that OSHA can and should play a central role in stemming this pandemic,” said David Michaels, an epidemiologist and professor at George Washington University who headed OSHA under President Barack Obama. “The law says employers must provide a safe workplace and requiring vaccination or testing is certainly one component of that.”

Several union groups signaled support for the new White House mandates. Randi Weingarten, president of the American Federation of Teachers, said the union stood in “complete support of this plan and of the administration’s effort to protect as many people as possible.”

Mary Kay Henry, president of the Service Employees International Union, said in a tweet that she was glad the mandate would require paid time off for workers to get vaccinated. “Vaccines are the most effective way to protect essential workers — but workers need adequate paid time off, protective equipment, pandemic pay and equitable access,” she wrote.

Jay Greene and Jeff Stein contributed to this report.