The U.S. announced late Thursday it is suspending 26 China-bound flights from the United States by four Chinese carriers after the Chinese government suspended some U.S. flights because of COVID-19 restrictions.

In a statement, the U.S. Department of Transportation (DOT) said the suspensions from September 5 to 28 will affect seven flights from New York to China and 19 China-bound flights from Los Angeles. The airlines include Xiamen, Air China, China Southern Airlines and China Eastern Airlines.

The DOT said the action is in response to China’s recent cancellation of 26 American, Delta and United Airlines flights under newly-revised COVID-19 regulations.

In its statement, the department said, as of August 7, China revised its COVID-19 policies, requiring airlines to suspend a flight if the number of passengers testing positive for COVID-19 reaches 4% of total passengers onboard. Previously, if up to nine passengers on a flight tested positive, a carrier could suspend a flight for two weeks or reduce the number of passengers to 40% of its capacity.

The U.S. DOT statement says China’s rules place “undue culpability” on airlines for passengers who present negative test results before boarding but test positive after arriving in China.

A spokesperson with the Chinese Embassy in Washington told the Reuters news agency the U.S. DOT action was “extremely irresponsible” and “groundlessly suspended Chinese airline flights.” The spokesperson said China’s COVID-19 “circuit breaker” measures were fair and transparent, applied both to Chinese and foreign airlines and were consistent with bilateral air transportation agreements.

Reuters reports China and U.S. regulators have been at odds regarding air services since the start of the pandemic. In January, the U.S. suspended 44 China-bound flights from the United States by the four Chinese carriers in response to China’s decision to suspend 44 flights on U.S. carriers.

The news agency says in August 2021, the U.S. DOT limited four flights from Chinese carriers to 40% passenger capacity for four weeks after Beijing imposed identical limits on four United Airlines flights.

Some information for this report was provided by the Associated Press, Reuters and Agence France-Presse.