The Biden administration is facing an internal debate over whether to impose vaccine mandates for air travel, with President Biden’s chief medical adviser, Anthony Fauci, saying he would support a mandate but the White House claiming a new policy isn’t forthcoming.

The potential of a mandate for domestic air travel would be fiercely opposed by Republicans and the travel industry and could add to the pushback Biden has received over his mandate on COVID-19 vaccines and testing for companies with at least 100 employees.

The White House sees the mandate on such businesses as politically popular, but it has run into opposition from GOP governors who have threatened to sue.

The administration could see a mandate to be vaccinated to fly as an issue that might find some support, but it also risks being seen as government overreach.

A flurry of questions was directed at White House officials this week after Fauci expressed his support for an air travel mandate.

“I would support that if you want to get on a plane and travel with other people that you should be vaccinated,” Fauci said on theSkimm podcast.

The idea isn’t off the table, White House press secretary Jen Psaki said on Thursday when asked about Fauci’s remarks.

“We haven’t taken options off the table, but I don’t have any updates to share with you at this point. Our focus is on implementation of the big steps we announced last week,” she said.

White House chief of staff Ron Klain on a podcast this week said a vaccine mandate for domestic air travel is being considered.

“It’s something we continue to look at. We want to kind of weigh the number of people that these requirements could vaccinate versus the burden on the vaccinated, having to show proof every time you go on to an airplane, having to wait on longer lines at TSA [Transportation Security Administration]. But I think it’s something we’ll look at as we continue to progress,” Klain said on "Pod Save America."

Klain argued vaccines to travel don’t make quite as much sense as vaccines to go to a workplace, as such a mandate would impose heavy burdens on those showing the verification and checking it.

“We think the most efficient vaccine requirements are ones that where people are kind of in a permanent situation, on the job, in the military, where they verify once, and then they’re verified in that scenario,” the chief of staff said.

Yet a number of restaurants, bars and music venues have imposed their own vaccine mandates, suggesting the requirement for plane travel, which confines people to close quarters, might make sense.

Jeff Zients, the White House coronavirus response coordinator, has said no measures are ruled out. He told reporters last week, when asked if the administration would impose a vaccine requirement or testing for domestic flights, “We’re not taking any measures off the table.”

Pressure to impose a mandate has already come from Congress.

Rep. Don Beyer (D-Va.) introduced legislation for all domestic airline and train travelers to show proof of vaccination or a negative COVID-19 test in order to travel.

Former President Obama’s Transportation secretary, Ray LaHood, said in a recent interview that the administration should push airlines to mandate vaccines for travelers and that if they won’t, the White House should impose those mandates itself.

White House officials reportedly debated the idea of vaccine mandates for just international travelers before Biden’s announcement last week. The announcement, which puts the spotlight on the private sector to get employees vaccinated or require testing, was sharply criticized by Republicans, with some vowing to take Biden to court. 

Republican governors such as Georgia Gov. Brian Kemp, Arizona Gov. Doug Ducey and South Dakota Gov. Kristi Noem have threatened legal action, while congressional Republicans such as House Minority Leader Kevin McCarthy (Calif.) argue people shouldn’t be coerced into vaccines.

Biden also announced that the Transportation Safety Administration will double the fines on travelers who refuse to wear masks. Psaki pointed to that update as one of the “bold, ambitious steps” the administration is taking when asked about support for vaccinations or negative tests for domestic air travel.

“Right now, our focus is on implementing those. Part of that was also doubling fines for people who were not wearing masks on planes — a step that we feel would help keep people safe on flights and reduce the spread,” she said on Thursday. 

The administration recently extended the federal mask mandate for all transportation networks through January. The mask mandate initially had a May expiration date but has been extended twice.

Republican lawmakers have bashed that policy. In July, Sen. Rand Paul (R-Ky.) introduced legislation to repeal the travel mask mandate and prohibit the federal government from imposing it. In June, other Republicans led by Sen. Ted Cruz (Texas) introduced a resolution calling for the mandate to be lifted.

The travel industry is already on high alert over the potential of a vaccine mandate for domestic air travel.

U.S. Travel Association President Roger Dow said this week it would be “extraordinarily difficult” to put such a mandate in place.

“[The] challenge is you’ve got upwards of 65 percent of the population vaccinated, and you have 35 to 40 percent that for some reason may not be able to be vaccinated, but yet they’re willing to do a COVID test and to show that when they walk in the door, that they are COVID-free,” he told reporters on Wednesday.

He said the trade group is “comfortable” with having people traveling to the U.S. being required to be vaccinated as a way to bring back international travel.

Delta Air Lines CEO Ed Bastian also said recently he doesn’t see vaccine mandates for domestic travel coming to the U.S. and that trying to figure out which travelers are vaccinated would “actually bottleneck the domestic travel system.” 

Airlines for America, which advocates for all major U.S. airports, said that while no policy change for domestic travel is coming soon, it would be concerned if that changes.

“We have been informed that there is no imminent policy proposal regarding domestic travel, and echo concerns expressed by government about the implementation and enforcement of such a policy. We remain in communication with the Administration and continue to lean into science to guide policies that prioritize the safety and wellbeing of the traveling public,” the group told The Hill in a statement.

The trade group has pushed for the U.S. to allow travelers who are fully vaccinated or present a negative COVID-19 test to travel to the U.S. as a way to lift international travel restrictions. The industry overall has pushed for the administration to ease restrictions on most non-Americans, especially those from the United Kingdom, who are currently barred from traveling to the U.S.

Zients has said the administration is working on a new system for regulating international travel and that it is considering vaccine requirements for foreign nationals traveling to the U.S.

Karl Evers-Hillstrom contributed to this report.