The White House on Wednesday backed President Biden one day after he said the decision to wear masks on public transportation is “up to” travelers — but still urged Americans to keep their face coverings on.

“The president was answering the question quite literally, which means right now — as you know — we are not implementing the mask mandate because of the court order, which we disagree with,” press secretary Jen Psaki told reporters.

“He is still abiding by CDC guidance, and we recommend Americans do that across the country,” she added, noting that staff on Air Force One all wore masks during their flight to New Hampshire on Tuesday.

“It is not a requirement, so people can choose, even as we recommend it,” Psaki later added. “But to be clear, we are recommending everyone wear masks on planes. That is what the CDC is recommending. That is the public health guidance we are following.”

Wednesday morning, the Centers for Disease Control and Prevention reiterated its recommendation to The Post, nearly 48 hours after US District Judge Kathryn Kimball Mizelle ruled the agency had overstepped its administrative boundaries in imposing the mask order.

“CDC continues to recommend that people wear masks in all indoor public transportation settings,” spokesperson Jasmine Reed said. “We will continue to assess the need for a mask requirement in those settings, based on several factors, including the US COVID-19 community levels, risk of circulating and novel variants, and trends in cases and disease severity.”

Mizelle, an appointee of former President Donald Trump, ruled on Monday that the CDC failed to properly explain its decision to impose the mask mandate or follow correct rule-making procedures.

Soon after the decision, the Transportation Safety Administration and a number of airlines announced that masks were optional on domestic and some international flights. Airports in places like Newark, Dallas, Atlanta, Los Angeles and Salt Lake City quickly followed suit, while other cities scrapped their mask requirement for mass transit.

Late Tuesday, the Department of Justice said that it will challenge Mizelle’s decision if the CDC determines the extension was “necessary for public health.”

When pressed on why the DOJ would not appeal the decision right away, Psaki said the Department is “waiting for that … final comment to take action.”

“The objective here is, of course, to appeal the 15-day extension, but also to preserve the CDC authority over the long term,” she said, “because we’ve noted from here, we expect there to be ups and downs in the pandemic and we certainly want the CDC to continue to have this authority.”

“I would expect to hear from the CDC very soon,” Psaki added. “And I don’t think it’s at the end of 15 days in terms of their expectation and ask for an appeal.”