Public health officials in California have confirmed the first known case of the Omicron coronavirus variant in the US.
The Centers for Disease Control and Prevention said on Wednesday the infected individual had recently returned from South Africa.
The traveller was fully vaccinated, has displayed mild symptoms so far and is currently self-isolating, the CDC said.
The US plans to impose fresh travel restrictions over the new variant, BBC reported.
International passengers are expected to soon be required to provide a negative test result from within 24 hours of their departure, US media reports have said.
President Joe Biden is expected to announce the stricter testing requirement and possible additional measures on Thursday.
The US and other countries have already imposed a ban on travel from eight African countries: South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi.