By a margin of just one vote, the General Assembly's legal committee approved a motion by Iran on behalf of the 57 Islamic nations to postpone U.N. action on cloning until the assembly session that starts in September 2005.
The 80-79 vote, with 15 abstentions, reflected the deep division in the 191-nation world body on how far a ban on cloning should go.
The postponement blocked the legal committee from voting on rival resolutions, one seeking a total ban and the other seeking a partial ban on human cloning.
The United States had lobbied intensively for a vote on a resolution sponsored by Costa Rica that would have established a working group to start drafting a treaty banning all forms of human cloning. That resolution was co-sponsored by about 50 countries.
A rival resolution introduced by Belgium called for a ban only on the cloning of babies, leaving the question of human cloning for research and medical experiments to individual countries. It was co-sponsored by 13 other countries, including Britain, China, Singapore and Japan, and supported by France, Germany and other nations.
"Of course we're disappointed at the outcome of the very close vote," said U.S. deputy ambassador James Cunningham. "We're disappointed that the proponents of the incomplete ban on cloning have been able to use a procedural device to prevent the international community from registering the significant majority that exists in favor of a total ban."
"It's particularly regrettable that it was by a margin of only one vote that we will be prevented from formally registering that more than 100 members of the United Nations favor the pursuit of the goal of a total ban on human cloning," Cunningham said.
The United States understood that some members of the Organization of Islamic Conference wanted more time to consider the issue, but he said "it's unfortunate that the other countries have been able to hide behind those concerns to deflect what would have been a significant majority in favor of our proposition."
Before the vote on the Iranian motion, the Belgian representative, Ambassador Jean de Ruyt, said that since it was impossible to reach consensus on a draft resolution, it would be better to delay consideration, leaving time to reach a compromise and perhaps for scientific research to shed new light on the debate.
Belgium stressed that a treaty on such a crucial issue should aim for universal acceptance, and that approval now of a resolution calling for a total ban would only create further division.
Opponents of a total ban had argued that since there was very strong international support for a worldwide ban on cloning babies, but less support for a ban on "therapeutic" cloning for research and medical purposes, the General Assembly should focus first on banning cloning for reproductive purposes.
Scientists supporting human cloning for medical purposes say they hope to use stem cells from human embryos to find cures for Alzheimer's, Parkinson's and other debilitating diseases. Stem cells, which are found in human embryos, umbilical cords and placentas, have not yet differentiated into any of the 220 cell types that make up the human body and so can divide and turn into any kind of cell in the body.
The Roman Catholic Church and anti-abortion groups say stem cell research is tantamount to murder because it starts with the destruction of a human embryo. The United States argues that there are already enough stem cell lines for scientists to use for research on diseases.
France and Germany, which launched the drive for a ban on cloning human beings that was then taken over by Belgium, said in a joint statement after the vote that they supported the postponement as "the lesser evil given the present lack of consensus."
Both countries said they consider it "paramount that this subject remains on the agenda of the General Assembly."
By Edith M. Lederer