Beijing on Wednesday criticised the US space agency NASA for what it termed "discriminative action" over a decision to exclude Chinese from a forthcoming science conference in the United States.

The National Aeronautics and Space Administration has announced that Chinese nationals will not be permitted to enter the Second Kepler Science Conference on exoplanets at California's Ames Research Center in November.

The decision sparked criticism by some prominent US astronomers. It also led the US congressman who wrote the law on which the restriction was based to call the decision "inaccurate".

In Beijing, Chinese foreign ministry spokeswoman Hua Chunying said she was aware of reports on NASA's decision.

"At the same time I have also noticed that the discriminative action by NASA has also met opposition" in the United States, she added.

"We think that these academic meetings should not be politicised."

The restriction is based on a law passed in 2011 and signed by President Barack Obama that prevents NASA funds from being used to collaborate with China or to host Chinese visitors at US space agency facilities.

The legal language was inserted into a funding bill by Congressman Frank Wolf, who chairs the House Subcommittee on Commerce, Justice, Science and Related Agencies.

The law bans NASA funds from being used to work "bilaterally in any way with China or any Chinese-owned company" or being "used to effectuate the hosting of official Chinese visitors at facilities belonging to or utilised by NASA," according to a copy of the legal text sent to AFP by Wolf's office.

Wolf's office wrote to NASA Administrator Charles Bolden on Tuesday saying the law "primarily restricts bilateral, not multilateral, meetings and activities with the Communist Chinese government or Chinese-owned companies.

"It places no restrictions on activities involving individual Chinese nationals unless those nationals are acting as official representatives of the Chinese government," it added.

Alan Boss of the Carnegie Institution for Science in Washington, the co-chair of the upcoming Kepler conference, issued a statement to attendees Tuesday, saying: "We find the consequences of this law deplorable and strongly object to banning our Chinese colleagues, or colleagues from any nation.

"We are pursuing other options that will allow participation by all interested scientists either in person or remotely."

An attempt to access NASA's website Wednesday was met with a notice saying it was unavailable "due to the lapse in federal government funding", a reference to the ongoing US government shutdown.