The US space agency NASA has blocked Chinese citizens with valid US visas from its facilities - a move that effectively bars them from working at one of the most respected space research centres.

Chinese nationals, who could only work at NASA as contractors or students contributing to research, found out on 5 September that they had lost all access to NASA's systems and facilities, Bloomberg news reported, citing sources.

NASA then confirmed this, stating that Chinese nationals would be restricted from using the agency's facilities, materials, and networks to ensure the security of our work.

China's accelerated space program has raised alarms in the US, ramping up the race between the two largest economies.

Chinese astronauts are already excluded from the International Space Station (ISS) because Washington has barred NASA from sharing its data with China.

The latest restriction adds to the decline in scientific collaboration between the two nations due to national security concerns, as the US and China compete for technological superiority.

The growing tensions have made it more challenging for Chinese students, particularly in science and technology, to obtain visas to study in the US.

Concerns over possible espionage have intensified scrutiny of Chinese nationals working in the US, particularly in academia and research fields.

Reports indicate that Chinese nationals had their access revoked suddenly, being informed of their restriction without prior notice. They were barred from attending meetings related to their work, whether in-person or virtual.

NASA's press secretary Bethany Stevens confirmed that the agency had taken internal action pertaining to Chinese nationals - including restricting physical and cybersecurity access to our facilities.

China's ambitions in space have been clear, as both Beijing and Washington race to send crews to the moon. We're in a second space race right now, stated NASA's acting administrator Sean Duffy, emphasizing the US desire to precede China in lunar exploration.

Legislators have stressed the urgency for the US to establish a presence on the moon before China, linking space capabilities to national security concerns and economic interests concerning lunar resource control.

The Moon is viewed as a potential source of valuable minerals, including rare earths, necessary for various modern technologies, increasing the stakes in this new space race.

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