President Joe Biden’s administration is working on a plan that would require most foreign visitors to be fully vaccinated before entering the country, according to a White House official.

The plan is part of an effort to lift travel restrictions currently imposed on various countries because of the coronavirus, the official told Reuters on Wednesday. While the White House won’t lift travel restrictions immediately, its hope is to “have a new system ready for when we can reopen travel,” according to the official.

The official noted that the plan will have “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,” Reuters reported. The U.S. has so far kept travel restrictions in place because of the rise of the Delta variant.

“Given where we are today … with the delta variant, we will maintain existing travel restrictions at this point for a few reasons,” White House press secretary Jen Psaki said in July. “The more transmissible delta variant is spreading both here and around the world. Driven by the delta variant, cases are rising here at home, particularly among those who are unvaccinated and appear likely to continue in the weeks ahead.”

Questions still remain regarding the plan, according to Reuters. The administration still needs to sort out key topics such as how to best implement such a requirement and whether vaccines being used in other countries – but not in America – would count for entry. (RELATED: President Biden Tells Americans To Expect More COVID Restrictions)

While the U.S. has kept restrictions in place, other countries like Canada are easing restrictions for Americans, Reuters reported. It isn’t immediately known when such a plan would be official, nor when it will be implemented.