The National Institutes of Health yesterday formally unveiled proposed guidelines for federally funded researchers who want to study human embryonic stem cells, which are obtained from discarded human embryos and have the potential to cure a variety of diseases.

The draft guidelines, which will be published today in the Federal Register for a 60-day public comment period, immediately triggered a flurry of dueling statements from patient advocacy groups, antiabortion activists and members of Congress, foreshadowing what several experts predicted would be a series of heated hearings on Capitol Hill.

As drafted, the guidelines would preclude publicly funded scientists from destroying embryos to obtain stem cells. But they would allow them to use embryonic stem cells obtained by privately financed scientists, so long as those scientists got the cells in ways the guidelines deem ethical.

For example, the embryos--typically left over from in vitro fertilization efforts--would have to be donated freely by mothers without compensation, and researchers who want to work on the cells could not be involved in asking permission for the embryos to be donated.

The guidelines drew quick praise from a Washington-based coalition of 34 patient advocacy groups, Patients' Coalition for Urgent Research, or CURe.

"Too many patients and their families across the country are struggling with devastating illnesses, and we have an obligation to do all we can to help them," said Daniel Perry, CURe's chairman. "At the same time, it's important that research goes forward in a way that meets the public's demand for ethically conducted science. Development of federal guidelines for stem cell research is the best means to both ends."

But the guidelines prompted immediate criticism from others.

"The human embryonic stem cell research being proposed by the NIH is illegal, immoral and unnecessary," said Sen. Sam Brownback (R-Kan.). "We must fight to cure disease. However, it is never acceptable to kill one innocent human being in order to help another. The responsible choice is for government to serve human life in ways that do not destroy life."

NIH Director Harold Varmus noted that the guidelines (posted on the Web at www.nih.gov/news /stemcell/draftguidelines.htm) are more restrictive than those recently recommended by the National Bioethics Advisory Commission, which would allow federally financed researchers themselves to derive stem cells from human embryos--an endeavor now illegal under the provisions of a rider to the Department of Health and Human Services appropriations bill.