Rep. Tulsi Gabbard, D-Hawaii, called Saturday for a halt on all flights from the United Kingdom into the U.S. amid increasing concern about a new, more infectious strain of COVID-19.

"The U.S. needs to temporarily halt all flights from the U.K. into the U.S. to stop more infectious mutation of COVID from entering the U.S. This should have been done days ago," tweeted Gabbard, a former presidential hopeful.

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Gabbard was reacting to new rules from the Centers for Disease Control and Prevention that require passengers from the U.K. to have proof of a negative COVID-19 test before their flight -- a move she said did not go far enough.

"Negative tests from passengers is not sufficient," she tweeted. "It's too little, too late."

The new rules about U.K. travel go into effect Monday. That is in addition to President Trump’s proclamation in March that barred the entry of foreign nationals who had visited the U.K. in the last 14 days from coming into the U.S. -- a move that the CDC said reduced travel from the U.K. to the U.S. by about 90%.

Other Democrats had welcomed the news, with New York Gov Andrew Cuomo calling it a "Christmas wish answered." He  previously announced that three airlines had agreed to require testing of passengers prior to boarding. 

New York City Mayor Bill de Blasio announced restrictions of his own -- with travelers from the U.K. to receive a quarantine order and a visit from a sheriff’s deputy ensuring they were complying.

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Some 40 countries have imposed travel restrictions on the U.K, where the new strain of virus has been documented. Britain briefly saw chaos at the Dover port in southeast England this week after France temporarily restricted travel to the European mainland, but later listed that restriction.

The Associated Press contributed to this report.