Klain did not immediately respond to an after-hours email from Fox News.

Republican members of Congress and state governors promised to challenge the mandate.

Arizona Republican Gov. Doug Ducey vowed to “push back” against Biden.

“This is exactly the kind of big government overreach we have tried so hard to prevent in Arizona — now the Biden-Harris administration is hammering down on private businesses and individual freedoms in an unprecedented and dangerous way,” Ducey wrote. “This will never stand up in court.”

Biden was praised by supporters for striking a more urgent tone. These supporters insist that one of the key reasons cases are spiking in the U.S. is due to the 80 million who have refused the jab. 


“My message to unvaccinated Americans is this: what more is there to wait for? What more do you need to see? We have made vaccinations free, safe, & convenient. The vaccine is FDA approved. Over 200 million Americans have gotten at least one shot. We have been patient, but our patience is wearing thin, and the refusal has cost all of us,” Biden said.

The Associated Press contributed to this report.