A group of scientists are proposing to conduct controversial experiments on the new H7N9 bird flu virus that may involve creating more potent strains to examine how they might spread among humans.
One participating Hong Kong scientist said the research was necessary to be one step ahead of the constantly mutating virus.
Professor Malik Peiris, head of virology at the University of Hong Kong, said the experiments were needed to achieve a more complete understanding of the virus or else scientists would be "working like they have one hand tied behind their back".
Critics worry about the danger of laboratory accidents and whether publishing findings from the research could offer a blueprint for bioterrorists.
Scientists who proposed the work explained, in a letter published in the journals Science and Nature, that researchers would be subject to review by biosafety committees and that high-standard risk mitigation plans would be applied.
The 22 scientists, from the US, the Netherlands, the UK and Hong Kong aim to develop more effective vaccines for H7N9 and identify mutations that lead to drug resistance. They hope to find out what makes the bird virus better adapted to mammals, more transmissible, and more able to cause diseases.
With much of the previous work on the virus done in Hong Kong and with all H7N9 human cases in China, Peiris said: "If Hong Kong is excluded, that would be very unwise."
Scientists in the group created an international controversy in 2011 by creating easier-to-spread strains of H5N1, another deadly kind of bird flu. It became transmissible among ferrets, which catch the same flu types as humans.
The H5N1 work was eventually published amid acrimonious debate, with findings including five mutations key to the increased transmissibility.
The new H7N9 was first identified in eastern China, with the first known human case of the virus reported in March. So far, 134 cases have been reported, resulting in 43 deaths.
A professor at the University of Minnesota, Michael Osterholm, said findings from the man-made H5N1 strains had not changed how health authorities monitor the virus in the wild. There was no scientific evidence that the mutations could predict an impending pandemic.
However, Peiris believed that knowing the possible changes that make the virus more aggressive would be useful. "If we see the changes in nature, we can respond quickly."
He did not think terrorists would want to make use of the research to make weapons, as the complicated work would be too much trouble.