By Alison Sider

The Trump administration further eased plans to restrict passenger flights by mainland Chinese airlines to the U.S. after China said it would permit more passenger flights by the US. airlines.

The U.S. Department of Transportation said Monday it would allow a total of four round-trip flights a week by Chinese airlines, double the level it had set earlier this month. The move came after Chinese authorities said they would allow both of the U.S. airlines seeking to return to China to operate two weekly flights each.

"We welcome this action by the Chinese government, as an important first step to fully restore air travel," the U.S. Transportation Department said in a statement.

The change announced Monday is further indication that both the U.S. and China are backing down from a standoff over airline service that threatened to halt scheduled passenger service between the two countries.

Delta Air Lines Inc. said Monday that it plans to fly from Seattle to Shanghai with a stop in Seoul next week. In July, it will fly once a week from Seattle and once from Detroit. Under an agreement with Chinese authorities, the airline will take passengers' temperatures before departure, a spokeswoman said.

"We are pleased to be re-entering the China market and are grateful to the U.S. government for its diligent efforts to ensure fair access to China for U.S. carriers," the airline said in a statement.

United, which has also sought to resume flights to China, said it welcomes efforts to resume service and aims to relaunch flights in the coming weeks.

The DOT earlier this month threatened to bar all flights by Chinese passenger airlines, saying Beijing had failed to approve resumption of these routes by U.S. airlines that suspended service to China due to the coronavirus pandemic. The ban would have gone into effect June 16, but wouldn't have affected cargo flights.

But Beijing quickly responded by saying it would ease flight restrictions on foreign carriers, allowing them one weekly flight to one city each, and DOT had in turn loosened its restrictions, saying it would allow two round-trip flights a week by Chinese airlines.

The new level set by the DOT could accommodate the current level of flying by Chinese passenger airlines. Four Chinese airlines-- Air China Ltd., China Southern Airlines Co., Xiamen Airlines and China Eastern Airlines Corp.--now operate scheduled passenger flights between the two countries, the Transportation Department said.

The U.S. Transportation Department said it remains concerned that U.S. airlines can't fully exercise their rights under a bilateral agreement that governs air service between the two countries and said it was prepared to revisit the restrictions again if Chinese authorities make further adjustments.

The Chinese Embassy in Washington didn't immediately respond to a request for comment.

Write to Alison Sider at alison.sider@wsj.com