Roman Catholic and conservative Protestant leaders condemned the first reported cloning of a human embryo, while other Christian and Reform Jewish leaders supported using the procedure to cure diseases.
Cardinal Theodore McCarrick, of the Catholic Archdiocese of Washington, said Massachusetts scientists who announced Sunday that they had cloned a six-cell embryo were playing God and reducing humans to spare parts.
"While we must encourage the scientific community to continue cutting-edge research, it must occur within ethical boundaries that respect all human life," he said Monday. Catholic teaching holds that life begins at conception, and a statement Monday from the Vatican reiterated that belief.
The Southern Baptist Convention, the nation's largest Protestant denomination, and the United Methodist Church, President Bush's denomination, both urged federal lawmakers to ban the research.
The Presbyterian Church (U.S.A.) and Reform Jewish leaders took a different position, supporting cloning to cure diseases but opposing it for reproductive purposes.
Jewish authorities teach that the primary responsibility is saving human life, even if some religious laws are broken, said Rabbi Richard Address, who oversees the bioethics program of the Union of American Hebrew Congregations. Also in the Jewish tradition, an embryo less than 40 days in development is considered unformed and not a fetus, he said.
It wasn't clear whether the cloned embryo that Worcester, Mass.-based Advanced Cell Technology announced it had created would have been capable of growing into a human being.
The embryo died even before any stem cells were produced. Stem cells -- the master cells that can turn into other body tissue like heart muscle and skin -- can be used to treat a variety of diseases, scientists say.
The Union of Orthodox Jewish Congregations of America has so far issued no statement on cloning. A panel of Orthodox rabbis and scientists are studying the research, union policy director Nathan Diament said.
Muslim scholars also are grappling with the issue. Some have supported using the research to grow healthy organs from other tissue, said Muzammil Siddiqi, director of the Islam Society of Orange County in California.
He said the Fiqh Council of North America, a panel of Islamic scholars who provide religious guidance, has issued no statements on human cloning.
"This is a new issue," he said.
In Washington, political opposition to human cloning is formidable. President Bush on Monday called Advance Cell Technology's announced cloning "morally wrong," and a bill awaiting debate in the Senate would criminalize human cloning.