The world faces a stark choice between banning cloning of humans or preparing ways to protect them from potential abuse or discrimination, a U.N. study said on Sunday.
Experts at the U.N. University's Institute of Advanced Studies said it would only be a matter of time before scientists manage to clone a human if governments do not impose a ban.
"Whichever path the international community chooses it will have to act soon -- either to prevent reproductive cloning or to defend the human rights of cloned individuals," said A.H. Zakri, head of the Institute, which is based in Yokohama, Japan.
"A legally-binding global ban on work to create a human clone, coupled with freedom for nations to permit strictly controlled therapeutic research, has the greatest political viability of options available," the study said.
Negotiations about an international ban on cloning collapsed in 2005 because of disagreements over whether to permit research cloning, also known as therapeutic cloning, to help treat diseases such as diabetes or Alzheimer's.
Almost all governments oppose human reproductive cloning and more than 50 have legislation outlawing cloning.
If governments decided against a ban, they should instead quickly prepare legal measures to protect human clones from "potential abuse, prejudice and discrimination", the study said.
Research cloning can produce tissues that are a perfect genetic match of a person and so help grow cells to treat diseases such as strokes, spinal injuries, diabetes, Parkinson's or Alzheimer's, according to the study, which was made available in Oslo.
The United Nations in 2005 agreed a non-binding declaration to ban human cloning but left many ambiguities. "The declaration in itself is not an adequate response," said Brendan Tobin, an author of the study from the National University of Ireland.
"This has left us in a situation where maverick scientists can carry on with their research and that is likely to lead to an eventual cloning," he told Reuters .
The authors said laws should grant clones full human rights to protect from discrimination.
Otherwise, opponents of clones in an inheritance dispute, for instance, might say that a clone and the person from whom their cells were grown should only get a half share each.
"In the same way as an identical twin is an individual, a clone would be an individual," Tobin said.
The report noted that clones have been made of mice, sheep, pigs, cows and dogs and that U.S. researchers last year achieved the first cloning of a primate -- a rhesus monkey embryo cloned from adult cells and then grown to generate stem cells.
It said that national bans on cloning could be skirted since researchers could simply move elsewhere.
"Disgraced South Korean medical researcher Woo Sook Hwang, whose human clone claims were unsubstantiated, reportedly continues his work in Thailand," the U.N. study said.