Excluding Chinese researchers from attending a conference of NASA, the US space agency, based on a law passed in early 2011, is "deplorable and wrong," organizers of the meeting said Wednesday, urging US Congress to relax "these unnecessary restrictions."

The meeting, scheduled for November at NASA's Ames Research Center in California, will be attended by researchers including those on both US and international teams working on NASA's exoplanet-hunting Kepler space telescope program.

But Chinese researchers, including those who worked at US universities and other institutions, were denied the opportunity to attend the meeting. NASA officials reportedly said the rejection was done in accordance with a law passed in 2011 that prohibits government funds from being used to host Chinese nationals at NASA facilities.

As a result, several prominent researchers, including Debra Fischer, who leads a research group at Yale University, and Geoff Marcy, an astronomy professor at the University of California, Berkeley, who is well-known for his pioneering work on exoplanets, are boycotting the conference.

Fischer told Xinhua that she learned about the legislation when her Chinese postdoctoral fellow, Wang Ji, had his application to the Kepler science meeting rejected.

"The meeting is about science and planets around stars, not about national defense. There is no classified information -- it is all publicly available data," she said. "I believed that it was not fair that some of our colleagues were barred from the meeting based on their country of origin."

The meeting organizers, the Scientific Organizing Committee ( SOC) of the Second Kepler Science Conference (KSC2), said in a statement that they learned about the law in late September while drafting the final agenda, and then they denied the registration of six Chinese researchers for the meeting.

"We find the consequences of this law deplorable and strongly object to banning our Chinese colleagues, or colleagues from any nation," the organizers said. "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."

"We support our colleagues who express their objections to this nation-based exclusion through whatever actions they choose. ... A strong argument for relaxing these unnecessary restrictions would be a public demonstration that open scientific inquiry and discussion is far removed from political concerns and devoid of threats to national security," they said.

The controversial law, which was initially crafted in 2011 by Frank Wolf, chairman of the House Appropriations subcommittee that funds NASA, had further modifications and restrictions added to a 2013 bill version.

In a letter to NASA Administrator Charles Bolden dated Tuesday, Wolf claimed that the law "primarily restricts bilateral, not multilateral, meetings and activities" with the Chinese government or Chinese-owned companies. He also said it "places no restrictions on activities involving individual Chinese nationals unless those nationals are acting as official representatives of the Chinese government."

"As such, the email from NASA Ames (explaining why Chinese students are not allowed to attend the meeting) mischaracterizes the law and is inaccurate," said Wolf. "NASA headquarters needs to send updated guidance to both the conference attendees and to the press to correct this misconception."

Alan Boss of the Carnegie Institution for Science, the cochair of the upcoming Kepler conference who signed the statement with several other scientists, called Wolf's comments a "positive" development in an email interview with Xinhua.

"Rep. Wolf's comments have had the positive effect of drawing NASA's attention to the problem with KSC II and attendance by our Chinese astronomer colleagues," Boss said. "We (the SOC) hope that NASA will find a solution that will allow them to participate in the conference."

The law introduced by Wolf has drawn criticism from some US analysts.

"I believe the current US prohibitions on cooperation with China in the area of human spaceflight are counterproductive," said Gregory Kulacki, a senior analyst with the US-based Union of Concerned Scientists' Global Security Program.

"They serve no beneficial political, economic or strategic purpose and may, in fact, harm the strategic interests of the United States," he told Xinhua earlier this year.

Kulacki said he was hopeful that with the passage of time, the US Congress "will adopt a more constructive set of policies that encourages greater contact and cooperation between space professional in China and the United States."