US President Joe Biden's administration is developing a plan to require nearly all foreign visitors to the United States to be fully vaccinated against Covid-19 as part of eventually lifting travel restrictions that bar much of the world from entering the United States, a White House official told Reuters on Wednesday.

The White House wants to re-open travel, which would boost business for the airlines and tourism industry, but is not ready to immediately lift restrictions because of the rising Covid-19 caseload and highly transmissible Delta variant, the official said.

The Biden administration has...