Some prominent American astronomers are boycotting a Nasa meeting next month on exoplanets due to a ban on attendance by Chinese scientists, experts told AFP.
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.
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," Marcy wrote in an email to the organisers.
The legal language that bans Nasa cooperation with the Chinese 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 assistant.
According to retired Nasa astronaut Leroy Chiao, who was born in the United States to Chinese parents, Wolf and several other lawmakers are engaged in a "whole campaign" to prevent US aerospace involvement with China.
"Unfortunately, I think they are uninformed and they have got outdated ideas," Chiao told AFP.
"Basically they are paranoid. They think China is trying to steal all of our technology."
Chiao said he supports better ties with China, based on the model of space cooperation that has existed between the United States and Russia since the 1990s.
"Cooperating in space helps the relationship between countries in other areas as well," he said.
Chiao said he applauded the scientists who are boycotting the astronomy conference, but said "they are a little misinformed, too."
"They think it is Nasa's fault. But Nasa has its hands tied because of the federal laws."
Certainly, Nasa is bound by the law. However, its administrator Charles Bolden earlier this year announced measures of his own to bolster security following a potential breach by a Chinese national working for a contractor at a Nasa facility in Virginia.
"The person in question no longer works at Langley," Bolden said at a hearing on March 20 before the House subcommittee that oversees funding for Nasa - the same one that Wolf chairs.
"I have ordered a complete review of the access which foreign nationals from designated countries are granted at Nasa facilities," Bolden added.
"I have ordered a moratorium on granting any new access to Nasa facilities to individuals from specific designated countries, specifically China, Burma, Eritrea, Iran, North Korea, Saudi Arabia, Sudan and Uzbekistan."
Pascale Ehrenfreund, a space policy expert at George Washington University, said tensions between the United States and China in scientific matters have persisted for years.
"Also at the International Astronautical Congress at the end of September in Beijing, China, US participation was scarce," she told AFP.
"I wonder why the conference was planned on Ames soil and not just outside the fence of Ames, like often done in the past," she added.
The Second Kepler Science Conference is scheduled for November 4-8 at Nasa Ames Research Center in Mountain View, California.
Co-chair Alan Boss of the Carnegie Institution for Science in Washington did not immediately respond to an AFP request for comment.