Around the globe there is nearly universal agreement that "reproductive cloning" - the effort to create cloned human beings - is wrong.
But when it comes to "therapeutic cloning" - developing stem cells from human embryos that could be used to treat diseases - opinion is far more divided. And that division is the controversial breach into which the United Nations legal committee will step Thursday in New York as it votes on a resolution to ban human cloning.
Although any UN vote would be largely symbolic, there is considerable global support for putting the international body on record as opposing reproductive cloning, which raises significant questions of both safety and ethics.
But reaching any kind of agreement on therapeutic cloning is likely to prove an elusive goal.
Cloning involves inserting animal or human DNA into an unfertilized egg whose own nucleus has been removed. In reproductive cloning the embryo would be placed in a surrogate mother and would develop into an exact physical replica of the DNA donor.
Therapeutic cloning produces and then destroys embryos only a few days old in order to reap their stem cells, which medical scientists believe eventually can be used to treat diseases such as juvenile diabetes, Parkinson's disease, hemophilia, spinal injuries, and stroke. Stem cells are like blank pages of a book which can be written upon, capable of becoming any kind of body tissue. They could be used to reproduce defective organs, for example.
The international community is sharply divided over the issue of therapeutic cloning, with three plans likely to be considered Thursday.
The Bush administration has strongly backed a Costa Rican proposal for a comprehensive ban on both reproductive and therapeutic cloning.
But a Belgian proposal to prohibit only reproductive cloning and leave individual countries free to either ban or regulate therapeutic cloning has also gathered strong support from countries such as Britain, Germany, and France.
At the same time, the Organization of the Islamic Conference, representing 57 Muslim countries, favors a postponement of the vote for one or two years to study the issue.
Animal cloning - which has been achieved with limited success, sometimes producing defective clones with various abnormalities - would not be considered in the ban debated Thursday.
But when it comes to human reproductive cloning, most within and without the global scientific community find the practice unpalatable. Concerns over the safety of the cloned individual (especially in light of the problems encountered in animal cloning) are paramount, as are the enormous difficulties in achieving such an operation.
While sheep and cows have been successfully cloned, primates, such as chimpanzees or gorillas, have not, indicating that human cloning may prove to be extremely difficult.
The Raelians, a quasi-religious group based in Switzerland, claim to have cloned five human babies in late 2002 and early 2003. But the group has never produced any conclusive proof of the births.
People have a "general moral queasiness" about reproductive cloning, says Kenneth Goodman, the founder and director of the bioethics center at the University of Miami. Some ethicists call it "the yuck factor." It creates human life "in a fundamentally novel way," and there's "something narcissistic" about it, he says.
That queasiness "points toward compelling moral reasons" against reproductive cloning. "It doesn't serve any of the traditional values of medical research" such as treating disease or reducing pain, he says.
From a Christian perspective, "I think you can make a case for reproductive cloning as 'hubris,' the sin of pride," says Suzanne Holland, who teaches courses on bioethics at the University of Puget Sound in Tacoma, Wash., and has co-edited a book on the stem-cell debate.
The debate over therapeutic cloning, however, much more closely mirrors the controversy over abortion. The crucial question is when life begins and whether a human life is being taken in the process of harvesting the stem cells. Many Christian groups, including the Roman Catholic church, argue that is the case.
But others - including most scientists - say the embryo at that point represents just one of the stages of the beginnings of life, and is not an individual human being.
"It's an ethical collision course" between those who take a "utilitarian" ethical approach, seeing the potential long-term good of therapeutic cloning, and those that say "you can never sacrifice any kind of life for the good of the whole," Ms. Holland says.
Little chance research will end
Even the scientific value of stem-cell research using embryos is disputed, though the vast majority of the American scientific community sees enough promise to favor ongoing research.
Some cloning opponents argue that stem cells taken from adults will prove to be a viable alternative to embryonic stem cells. But while a few scientists do hold out great hope for adult stem-cell research, "most scientists would say adult stem cells are not a substitute for embryonic stem cells," says Mark Rothstein, who directs the Institute for Bioethics, Health Policy, and Law at the University of Louisville.
Some scientists argue that the word "cloning" has eerie science-fiction connotations and perhaps scares the public more than is necessary - especially when it comes to therapeutic cloning.
"A lot of people are confused by this debate," says Mr. Goodman. For example, he says, if you say you have placed a bit of human skin cell into an egg and then five days later harvested the stem cells that have grown, people will say that's fine. But if you call it "cloning," people are likely to oppose it. "The name has become an emotional sledgehammer," he says
A move to delay a cloning ban for two years at the UN Thursday would actually be aimed at waiting out the Bush administration, says Thomas Jacobson, who follows the United Nations for Focus on the Family, a private Christian organization in Colorado Springs, Colo., that favors an immediate comprehensive UN ban.
The hope of proponents of cloning would be that after the 2004 elections a different US president might not oppose therapeutic cloning.
Ethicists agree, however, that even if the UN were eventually to ban cloning, research is unlikely to end. The best the UN could hope for would be an international treaty, which nations would have the right to sign on to - or not.
"I think it's a good impulse for the world to try to come together and speak with one mind about what we'd like to do about [cloning]," Holland says. "But I don't think it can be outlawed. It's going to happen somewhere if somebody wants to do it."
1938 Cloning envisioned. Dr. Hans Spemann (Germany) proposes removing the nucleus from an unfertilized egg and replacing it with the nucleus of a differentiated cell.
1953 Structure of DNA is discovered.
1970 A British scientist clones a frog by transplanting a tadpole cell into a frog egg.
1984 In Denmark, a lamb is cloned from a developing sheep embryo cell. The experiment is repeated by scientists who clone a variety of other animals.
1996 Dolly the sheep, the first mammal cloned from a cell of an adult animal, is produced in Scotland.
1999 Human chromosome 22 is the first to be completely sequenced.
2000 The same company that produced Dolly clones pigs from adult cells.
2001 President Bush, cautious about the use of stem cells taken from human embryos, limits the type of stem-cell research that can receive federal funding.
2001 The first household pet, a calico cat, is cloned in the US.
2001 Advanced Cell Technology in Worcester, Mass., announces that through cloning they have produced an embryo with human DNA that has grown to the six-cell level. The announcement draws criticism from President Bush and raises new ethical questions.
2003 The Human Genome Project - an effort to map and sequence all the human genes - is officially complete, contributing to the progress of cloning research.
Sources: Doegenomes.org, infoplease.com, and news accounts.