Prominent US astronomers are boycotting a NASA meeting next month on exoplanets because Chinese scientists have been banned from attending, experts say.

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 host Chinese visitors at US space agency facilities.

The final frontier: China's first female astronaut Liu Yang leaves the re-entry capsule of a Shenzhou-9 spacecraft in Inner Mongolia in June last year. Credit:Xinhua

Among those leading the boycott are Debra Fischer, an astronomy professor at Yale University, and Geoff Marcy, an astronomy professor at the University of California, Berkeley.

''In good conscience, I cannot attend a meeting that discriminates in this way. The meeting is about planets located trillions of miles away, with no national security implications,'' Professor Marcy wrote in an email to the organisers.