NASA is trying to resolve an international spat over banning Chinese scientists from a planetary conference, but efforts to do so are being hampered by the US government shutdown, a meeting organizer said on Wednesday.

Some leading US astronomers have vowed to boycott the conference next month at a US space agency facility in California because six Chinese scientists were told they could not attend.

China's Foreign Ministry has described the move as discriminatory and said academic meetings should remain free of politics.

Organizers of the Second Kepler Science Conference from Nov 4 to Nov 8 said they were acting on a March order for a moratorium on visits to NASA facilities by citizens of several nations, including China.

Republican Congressman Frank Wolf questioned the ban on Tuesday and said 2011 legislation that he authored restricted space cooperation with the Chinese government and Chinese companies but not individuals.

The moratorium and other additional security measures were issued earlier this year by NASA administrator Charles Bolden following a potential security breach at a NASA facility in Virginia by a Chinese citizen and should have been lifted by now, Wolf said.

Jiang Bo, a Chinese national, who worked at NASA Langley Research Center, was arrested before boarding an airplane at Dulles International Airport in March.

An affidavit said Jiang failed to disclose all of the electronics he was taking with him. Several attempts by AFP to reach NASA spokespeople went unanswered.

Jiang was accused of taking a NASA laptop to China and though US authorities questioned him as a Chinese spy, investigators said Jiang did not leak any classified information. Jiang plead guilty to a misdemeanor charge for violating NASA rules after researchers found images belonging to NASA on the confiscated computer.

"The NASA folks are not legally able to read their e-mails. This is the major reason the brouhaha continues, in my opinion," said conference co-organizer Alan Boss of the Carnegie Institution for Science.

The US government shutdown has sent 97 percent of the space agency home without pay along with hundreds of thousands of federal workers across the country.

"Representative Wolf's statement has caught the attention of NASA officials, who are working now to see if the problem can be solved," Boss said.

"This is all happening in real time, though with the furlough still in place, this effort is an uncertain one," he added.

"I believe this problem would have been solved were it not for the federal shutdown preventing communication with NASA."

Boss and other members of the organizing committee said in a statement on Tuesday, "We find the consequences of this (moratorium) deplorable and strongly object to banning our Chinese colleagues, or colleagues from any nation".

Had they been aware of the restrictions on holding the meeting at NASA's Ames facility and inviting Chinese scientists, they would have pursued an alternate venue, he added.

"The policies that led to this exclusion have had a negative impact on open scientific inquiry. We feel very strongly that it is wrong to exclude scientists, on the basis of nationality, from a meeting that welcomes free and open exchange of scientific ideas."

One of the leading astronomers who vowed to boycott, Debra Fischer of Yale University, said that one of her post-doctoral students was among those whose application was denied.

AFP—China Daily

Zhao Yanrong contributed to this story.