The US will restrict travel from South Africa and seven other southern African countries to try to contain a new coronavirus variant spreading there.
From Monday, only US citizens and residents will be allowed to travel from the region.
This follows a similar flight ban imposed by the EU and the UK. Canada is also introducing travel restrictions.
The World Health Organization (WHO) earlier declared the new variant to be “of concern”, naming it Omicron.
US officials said flights from South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique and Malawi will be blocked, mirroring earlier moves taken by the EU. The ban will come into effect on Monday.
In a statement, President Joe Biden called the move a “precautionary measure” taken until more is known about the variant.
The Omicron variant was first reported to the WHO from South Africa on 24 November, and has since been identified in other countries.
South Africa’s health ministry has criticised the rush to impose new travel restrictions, calling them “draconian”, and contrary to WHO guidance.
Scientists say they still have much to learn about the virus’s new mutations, and the WHO has said it will take a few weeks to understand the impact of the new variant, as experts work to determine how transmissible it is.
The WHO on Friday said preliminary evidence suggested the new variant carried a higher risk of reinfection than other variants.
Scientists have said it is the most heavily mutated version yet, which means Covid vaccines, which were designed using the original strain from Wuhan, China, may not be as effective.
Most of the cases in South Africa have been from its most populated province, Gauteng, of which Johannesburg is the capital city.
The WHO has warned against countries hastily imposing travel restrictions, saying they should look to a “risk-based and scientific approach”.
South African Health Minister Joe Phaahla told reporters that the flight bans against the country were “unjustified”.
The bans already appear to be causing confusion at a number of airports. Passengers on a plane traveling from Cape Town to Manchester via Amsterdam told the BBC that they were held on the tarmac at Schiphol Airport in the Dutch capital for four hours, before eventually disembarking to take PCR tests.
Meanwhile, the flight bans threaten to separate families over the festive season.