PORTSMOUTH, N.H. (Reuters) -U.S. President Joe Biden said on Tuesday that "it's up to them" when asked whether people should keep wearing masks on airplanes, a statement at odds with his administration's official guidance.

A federal judge in Florida on Monday ruled that the 14-month-old directive was unlawful, overturning a key presidential effort to reduce the spread of COVID-19.

The Biden administration may appeal the decision, White House spokesperson Jen Psaki said on Tuesday. And the U.S. Centers for Disease Control and Prevention still advises people to wear masks on public transit, as Psaki noted shortly before Biden's comment.

"We're continuing to encourage people to wear masks," Psaki told reporters on Air Force One.

After landing in New Hampshire, a short while later, Biden, asked whether people should continue to wear masks on planes, said, "It's up to them."

Monday's court decision, which came in a lawsuit filed last year in Tampa, Florida, means the CDC's public transportation masking order is no longer in effect, a U.S. official said. [ ]

It comes as COVID-19 infections are rising https://graphics.reuters.com/world-coronavirus-tracker-and-maps/countries-and-territories/united-states/ in the United States, and more than 400 people are dying daily from the airborne disease, based on the latest seven-day average.

Justice Department officials are weighing whether to appeal, Psaki said, and the review will take a couple of days.

That ruling followed a string of judgments against Biden administration directives to fight the infectious disease that has killed nearly 1 million Americans, including vaccination or COVID testing mandates for employers.

"Public health decisions shouldn't be made by the courts. They should be made by public health experts," Psaki said.

(Reporting by Jeff Mason and Trevor Hunnicutt; editing by Jonathan Oatis and Heather Timmons)