The US will require airline passengers from the UK to produce a negative Covid-19 test before their flight, in response to a new variant of coronavirus.
It is the latest country to announce new travel restrictions because of the variant spreading in the UK and elsewhere.
Airline passengers from the UK will need negative tests within three days of their trip and to provide the results to the airline, the Centres for Disease Control and Prevention said in a statement.
The agency said the order will come into effect on Monday.
Airlines must deny boarding to any passenger who does not get a test, the CDC said.
The agency said because of travel restrictions in place since March, air travel to the US from the UK is already down by 90%.
Last weekend, Prime Minister Boris Johnson said the new variant of coronavirus seemed to spread more easily than earlier ones and was moving rapidly through England. Dozens of countries have since barred flights from the UK.
But he stressed there is “no evidence to suggest it is more lethal or causes more severe illness”, or that vaccines will be less effective against it.
This week, New York governor Andrew Cuomo said three airlines with scheduled flights from London to New York — British Airways, Delta and Virgin Atlantic — had agreed to require passengers to take a test before they get on the plane.
United Airlines on Thursday agreed to do the same for its flights to Newark, New Jersey.
The UK has been under considerable pressure since the word of the new variant was made public. Some 40 countries imposed travel bans, leaving the nation increasingly isolated, after Mr Johnson warned that the new variant might be 70% more contagious
France relaxed a coronavirus-related ban on trucks from Britain on Tuesday after a two-day standoff that stranded thousands of drivers and raised fears of Christmas food shortages in the UK.
French authorities, who imposed the ban to try to protect the continent from the new variant, said delivery drivers could enter by ferry or tunnel provided they showed proof of a negative test.
Russian authorities later ordered those arriving from the UK to quarantine for two weeks.
Earlier this week, Moscow suspended direct flights from the UK, and the new order from the Rospotrebnadzor sanitary safety agency starts from Saturday.