Beijing reacted after NASA chief Bill Nelson raised concerns over China's "landing on the moon and saying: 'It's ours now and you stay out'."
Beijing has rejected a warning from the chief of NASA that China might "takeover" the moon as part of a military programme, saying it has always called for the building of a community of nations in outer space.
"This is not the first time that the head of the US National Aeronautics and Space Administration has ignored the facts and spoken irresponsibly about China," said a Chinese foreign ministry spokesperson on Monday.
"The US side has constantly constructed a smear campaign against China's normal and reasonable outer space endeavours, and China firmly opposes such irresponsible remarks," added Zhao Lijian.
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 Administrator Bill Nelson told German newspaper Bild in an interview published on Saturday that China's space programme was a military one and that China had stolen ideas and technology from others.
"We must be very concerned that China is landing on the moon and saying: 'It's ours now and you stay out'," the US space agency chief added.
To the moon
China has stepped up the pace of its space programme in the past decade, with exploration of the moon a focus.
The country made its first lunar un-crewed landing in 2013 and expects to launch rockets powerful enough to send astronauts to the moon towards the end of this decade.
NASA, under its Artemis programme, 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 un-crewed missions to the moon's south pole some time this decade.