A view of signage leading to one of the testing centers at Heathrow Airport on December 22, 2020 in London, England.Joseph Okpako | Getty Images News | Getty ImagesThe United States will begin requiring people flying in from the U.K. to test negative for Covid-19 no more than 72 hours before departure, the CDC said in a late Thursday statement.The CDC said passengers would have to provide airlines with documentation of their lab results from either polymerase chain reaction (PCR) and antigen tests.Airlines would also have to confirm that passengers have tested negative before boarding, the agency said. They would also have to block passengers from boarding if they refuse to take a test.The CDC said President Donald Trump will sign the order on Friday, Christmas Day. It will go into effect starting Monday.Earlier this week, the U.K. said it identified a new strain of Covid-19 that appears to spread more quickly. Dozens of countries swiftly restricted travel from the U.K. in efforts to prevent the strain from entering their own borders. This is breaking news. Please check back for updates.