Nevada governor Steve Sisolak has said that large event operators will be allowed to opt out of the state's mask requirements if they can verify that attendees are fully vaccinated against Covid, Reuters reports.

Those partially vaccinated and children could still attend provided they wear a mask, he said.

Sisolak said the exception was “not a mandate”, but an option available for those operating venues with the capacity of 4,000 or more.

His announcement comes after San Francisco and New Orleans joined New York City in ordering patrons to show proof of vaccination to enter restaurants, gyms and other venues in an effort to stem the fast-spreading Delta variant.