JIUQUAN -- China's space workers are paying close attention to the two in-orbit American astronauts who have been delayed returning to Earth and wish for their safe return, said a spokesperson with the China Manned Space Agency (CMSA) on Tuesday.

"We appreciate NASA's high regard for the safety of its astronauts, and at the same time, we extend our best wishes for the safe return of the two astronauts," CMSA spokesperson Lin Xiqiang told a press conference at the Jiuquan Satellite Launch Center in Northwest China.

Two NASA astronauts were left behind at the International Space Station after Boeing's troubled capsule returned to Earth in September. Their original itinerary on the test flight was eight days, but they will wait for a ride back with SpaceX in late February next year.

Lin said that manned spaceflight activities are always fraught with risks and challenges, and the safety of astronauts is always the top concern for governments and people worldwide.

Lin said China ensures that no problems are brought to space and continuously optimizes emergency response plans to mitigate threats to its astronauts, such as space station leakage caused by impacts from space debris.

Since the space station's initial operation phase, the time available for astronauts to respond to emergencies has increased fivefold, Lin said.

The Shenzhou XX manned spacecraft and a Long March 2F rocket are now on standby at the final assembly plant in the Jiuquan Satellite Launch Center. He added that they can swiftly convert to a launch state to carry out emergency rescue missions for astronauts in the space station.