A team of scientists in Norfolk, Va., has become the first group of researchers to create human embryos in the lab for the sole purpose of harvesting their stem cells.

Until now, scientists had gotten stem cells only from excess embryos donated from infertility treatments. In such cases, potential donors would be approached and informed that their frozen embryos, which would normally be discarded after successful treatment, could instead be used for stem-cell research.

The new procedure, conducted by researchers at the Jones Institute for Reproductive Medicine in Norfolk, drew criticism from religious conservatives opposed to embryo research.

"I think this is a cautionary tale against starting down the slope," Richard Doerflinger of the National Conference of Catholic Bishops told The Washington Post in Wednesday's edition.

President Bush has said he will soon decide whether to allow taxpayer dollars to be used for research on embryonic stem cells. He is under pressure from both patient groups that favor the research and opponents who feel the work is inherently unethical.

The Norfolk scientists said several review panels had looked at the ethical implications and concluded that the approach was at least as ethical as using spare frozen embryos, which would normally otherwise be discarded after successful fertility treatment.

"At one level, it's cleaner [ethically]" than using leftover embryos, said Sean Tipton, spokesman for the American Society of Reproductive Medicine. "There's no question as to what you're going to do with these embryos. You're going to the individuals upfront."

The group extracted eggs from a dozen women, who signed consent documents and were paid $1,500 to $2,000 each, according to William Gibbons, a reproductive endocrinologist who was not involved in the work.

Of the 162 eggs collected and inseminated by donor sperm, 50 embryos were successfully created. The researchers destroyed 40 of those to get the stem cells that resided inside. The work was done with private funds.

The results appear in the July issue of the journal Fertility and Sterility, published Wednesday. The study began in 1997 and concluded last July.

Interest in embryonic stem cells centers around their ability to generate other tissues of the body. Doctors hope using stem cells could possibly cure diseases as Alzheimer's, diabetes, cancer, Parkinson's and spinal-cord injuries.

Despite the medical value of the research, opposition to use and destruction of embryos is likely to remain strong.

"It's still killing a human being," Mary Petchel, president of the Tidewater chapter of the Virginia Society for Human Life, told The Virginian-Pilot of Norfolk.

The Associated Press contributed to this report