Chinese scientists hope the country's first group of genetically modified (GM) cloned piglets will have organs that are suitable to be transplanted into humans.

They expect the special pigs will be born within the next six months.

"The genetically modified piglets could bring hope to people who are in need of organ transplants but have failed to find a donor," said Zhao Zijian, head of the Metabolic Disease Research Center at Nanjing Medical University.

Zhao's research group has been studying GM technology since 1998 in the hope of replacing the gene in pigs that causes humans to reject transplanted pig organs, the Nanjing-based Yangtze Evening Post quoted Zhao as saying on Monday.

"Just as people with different blood types cannot accept blood transfusions from one another, pig organs were rejected by all human recipients before I replaced a certain sugar molecule with a human gene," said Dai Yifan, deputy director of the research center.

Dai successfully bred the so-called transplantation-friendly GM pigs in a laboratory at Revivicor Inc in the United States and took cells back to China earlier this year from which he plans to clone thousands of pigs.

The first brood will be born in five or six months in Nanjing, capital of Jiangsu province. They will then undergo additional experiments to see if they are suitable donors of hearts, kidneys and livers.

The scientists are currently constructing sterile pigsties that are "as clean as an operating room", Dai said. "The sterile environment will mean there are no viruses on the pigs that could cause diseases among humans."

However, transplant surgeons expressed doubts about the project.