WASHINGTON (AP) — The United States moved Friday to block 44 flights to the U.S. by Chinese airlines in retaliation for China forcing the cancellation of flights by U.S. airlines.

The Transportation Department order affecting four Chinese airlines is the latest development in a long-running dispute over COVID-19 restrictions.

China previously barred some inbound flights by Delta Air Lines, United Airlines and American Airlines after passengers on earlier flights tested positive for the virus. The U.S. maintains that China's actions violated a treaty over access to each country by the other country's airlines.

The Transportation Department said that China's move to block 44 flights by U.S. carriers was "adverse to the public interest and warrant proportionate remedial action by the department."

The department said that China's regulations are unfair because passengers who test negative for the virus before their flight but positive up to seven days later can result in future flights being canceled.

The U.S. order limits flights between Jan. 30 and March 29 by Air China, China Eastern Airlines, China Southern Airlines and Xiamen Airlines.

The dispute over flights goes back to 2020 and the early days of the pandemic. In 2020, the Trump administration backed down from a threat to block four Chinese airlines after China agreed to let United and Delta operate a limited number of flights.

The spat flared again in August 2021, when the U.S. Transportation Department limited the number of passengers on some Chinese flights to the U.S. after China imposed similar limits on United. In December, Delta blamed new Chinese restrictions when a plane bound for Shanghai returned to Seattle.