The Biden administration is currently developing a “phased” plan requiring all foreign nationals traveling to the U.S. to be fully vaccinated before entry, with “limited exceptions,” according to a White House official.

Federal interagency working groups are “developing a policy and planning process to be prepared for when the time is right,” the official also said. Reuters first reported the development of an expected vaccination requirement for most international travelers. 

“The interagency working groups are working to develop a plan for a consistent and safe international travel policy, in order to have a new system ready for when we can reopen travel. This includes a phased approach that over time will mean, with limited exceptions, that foreign nationals traveling to the United States (from all countries) need to be fully vaccinated,” the official told CBS News. “Currently, the interagency working groups are developing a policy and planning process to be prepared for when the time is right to transition to this new system.”

The official said that the administration is united in wanting to reopen international travel in a way that’s safe and sustainable. Because of the COVID surge largely caused by the delta variant, the U.S. is maintaining existing travel restrictions. 

It’s not yet clear when the vaccination requirement for foreign nationals will begin, or what exemptions may apply.

Other countries are already requiring foreign travelers to be fully vaccinated before their arrival. The U.S. currently bans foreign nationals from certain countries with high COVID-19 transmission rates from traveling to the U.S., but has not yet prioritized travelers based on their vaccination status. 

Meanwhile, some localities in the U.S. are beginning to require vaccinations for many indoor activities. New York City will require proof of vaccination for patrons to enter indoor bars, restaurants and gyms.