China on Monday rejected as an irresponsible smear a warning from the chief of NASA that China might "take over" the moon as part of a military program, saying it has always called for the building of a community of nations in outer space.

China has stepped up the pace of its space program in the past decade, with exploration of the moon a focus. China made its first lunar uncrewed landing in 2013 and expects to launch rockets powerful enough to send astronauts to the moon towards the end of this decade.

"We must be very concerned that China is landing on the moon and saying: 'It's ours now and you stay out'," NASA Administrator Bill Nelson told German newspaper Bild in an interview published on Saturday.

The U.S. space agency chief said China's space program was a military one and that China had stolen ideas and technology from others.

"This is not the first time that the head of the U.S. National Aeronautics and Space Administration has ignored the facts and spoken irresponsibly about China," said Zhao Lijian, a spokesman at the Chinese foreign ministry.

"The U.S. side has constantly constructed a smear campaign against China's normal and reasonable outer space endeavors, and China firmly opposes such irresponsible remarks."

China has always promoted the building of a shared future for humanity in outer space and opposed its weaponisation and any arms race in space, he said.

NASA, under its Artemis program, plans to send a crewed mission to orbit the moon in 2024 and make a crewed landing near the lunar south pole by 2025.

China is planning uncrewed missions to the moon's south pole some time this decade.