At least three of the six Chinese researchers who are originally banned from a forthcoming NASA conference on distant planets said Wednesday they have got security clearance from the space agency and are now welcome to attend the meeting.

"We are very pleased to inform you that your review for clearance has been completed," according to a copy of the invitation letter sent to Xie Jiwei, one of the initially banned researchers from China's Nanjing University.

"You have been accepted for attendance at the Second Kepler Science Conference ... We hope you will be able to join us," said the letter, signed by Dawn Gelino and Mark Messersmith, co-chairs for the conference.

Xie told Xinhua he has decided to fly to the meeting, which is scheduled for November at NASA's Ames Research Center in California.

"This event will set a benchmark on how to deal with these kinds of incidents in the future," Xie said. "We now have a better reference solution."

Another Chinese researcher, Zhao Guo, a PhD student of the Georgia State University, said he has already booked a flight for the meeting. "The ban didn't affect me much," Guo said, "However, I'm still very thankful for those American astronomers who have a strong sense of justice."

A third Chinese researcher, who refused to be named, also confirmed that he was cleared for attendance and that he will present his findings about planets outside our solar system at the Kepler conference.

The initial decision to block the six sparked a boycott of the meeting from several prominent American scientists, including Professor Debra Fischer of Yale University, and Professor Geoff Marcy of the University of California, Berkeley.

The ban was the result of a controversial law passed in 2011 that prohibits government funds from being used to host Chinese nationals at NASA facilities. However, in response to the boycott, Congressman Frank Wolf asserted early this month that it places no restrictions on activities involving Chinese individuals "unless those nationals are acting as official representatives of the Chinese government."

On Tuesday, NASA spokesman Allard Beutel told Xinhua that the initial decision was "unfortunate" and based on "a misinterpretation" of the government policy.

"The scientists of Chinese origin who initially were excluded .. . now are able to apply," Beutel said. "The interpretation was clarified, and the decision corrected once the federal government reopened last Thursday."

Gregory Kulacki, a senior analyst with the US-based Union of Concerned Scientists' Global Security Program, believed that recent problems arising from the ban should be served as a wake-up call for "a few individuals within the United States Congress, in particular Congressman Frank Wolf," who crafted the law.

Kulacki said the language of the law is "so broad, and the legal and financial penalties associated with potential violations so threatening, that even US organizations not directly administered by NASA are afraid to reach out to colleagues in China."

He warned that until the legislation is removed, these kinds of incidents will "remain a constant feature" of US-China relations in space.