CHICAGO (Reuters) -United Airlines and Delta Air Lines are requiring all passengers on flights from the United Kingdom to the United States to present a negative COVID-19 test taken within 72 hours of departure. The decision follows the emergence of a highly infectious new coronavirus variant in Britain that has prompted many countries to shut their borders to travelers from there. Delta’s policy, expanded from its decision on Monday to require the screenings on UK flights to New York’s John F. Kennedy International Airport, is effective Dec. 24, while United’s requirement begins Dec. 28. Passengers will be asked to show proof of a negative molecular COVID-19 test or antigen test, and same-day, pre-flight rapid tests will be available for ticketed passengers at a Heathrow testing center. Earlier this week members of a White House coronavirus task force recommended that the U.S. government impose COVID-19 screenings for passengers from Britain. But the Trump Administration decided not to take action, people briefed on the decision told Reuters. The administration has repeatedly refused to issue mandates for many federal COVID-19 safety policies for air travel, leaving any requirements to the airlines. On Monday, the three airlines that fly from London to JFK - Delta, British Airways and Virgin Atlantic - agreed to a request from New York Governor Andrew Cuomo that they screen passengers from Britain. Delta also flies between London and Atlanta. United currently has four daily flights from London Heathrow to Chicago, Newark, N.J., Washington Dulles and San Francisco. It announced earlier this month that it will operate only two daily flights in January, to Chicago and Newark. U.S. airlines have already drastically scaled back flying to the United Kingdom, as well as the rest of Europe. American Airlines, with one daily flight between London and Dallas, has yet to announce any test requirements.