“These are conversations that are ongoing,” a senior CDC official said.

The Biden administration is “actively looking” at requiring COVID-19 tests before domestic flights, a senior Centers for Disease Control and Prevention official said on Tuesday.

“These are conversations that are ongoing,” CDC Director for the Division of Global Migration and Quarantine Marty Cetron told reporters, “and looking at what the types and locations of testing might be. We’re actively looking at it.”

This would be an expansion of the administration’s mandatory testing requirement for U.S.-bound travelers that took effect on Tuesday. All travelers flying into the U.S. must now provide proof of a negative COVID-19 test, taken no more than three days before their flight, or they will be denied boarding.

The order was initially announced by the CDC on Jan. 12 and formalized in an executive order President Joe Biden signed last week.

“We urge folks to postpone their trips if they’re able,” acting Assistant Secretary of Consular Affairs Ian Brownlee said Tuesday, “and if they absolutely must travel to equip themselves with information.”

Brownlee warned travelers will be responsible for covering their own lodging and medical costs if they test positive or cannot get a test while overseas.

“The bottom line message is this is really not a time for people to be engaging in discretionary travel, and that all travel should be postponed until we get a better handle on getting this virus under control and accelerate our vaccination strategies,” Cetron said.