WASHINGTON -- The draft guidelines released Friday by the National Institutes of Health -- requiring federally funded scientists to use only stem cells culled from fertility clinic embryos that otherwise would be thrown away -- is an unpopular move on both sides of the issue.
The rules have tempered a celebration by scientists who cheered when President Obama ended restrictions on federally funded embryonic stem cell research last month, and anti-abortion groups are concerned about political motivations.
The guidelines reflect rules with broad congressional support, excluding more controversial sources such as cells derived from embryos created just for experiments.
"We think this will be a huge boost for the science," said Acting NIH Director Raynard Kington. "This was the right policy for the agency at this point in time."
But the limit will disappoint some researchers who had hoped to use a broader variety of cells.
Scientists are trying to harness embryonic stem cells -- master cells that can morph into any cell of the body -- to one day create replacement tissues and better treat, possibly even cure, ailments ranging from diabetes to Parkinson's to spinal cord injury.
Those cells can propagate indefinitely in lab dishes, but initially culling them does destroy a days-old embryo, a result strongly opposed by many on moral grounds. The Bush administration had limited taxpayer-supported research to a handful of embryonic stem cell "lines" or groups, a policy that the NIH said was slowing the pace of potentially groundbreaking science.
Anti-abortion groups were not pleased with the new guidelines.
"The Obama administration today slides further down the slippery slope of exploiting non-consenting members of the human species -- human embryos," the National Right to Life Committee said in a statement. "NIH today badly understates the scope of the longstanding law that actually prohibits funding of research that creates or harms human embryos, including all creation of human embryos by cloning."
"We believe that today's action may be part of a 'bait-and-switch' strategy, under which Democratic leaders in Congress will suddenly bring up new legislation that they will claim codifies today's NIH action, but which will in fact authorize further expansions involving the deliberate creation of human embryos for use in research, by human cloning and other methods," the group added.
Kington refuted the idea that the guidelines were politically motivated.
"We were given the direction from the president to create guidelines that would allow the agency to fund scientifically worthy and ethically responsible research," he explained. "We make decisions like this all the time."
Obama last month ended the Bush limit and widened the field -- but he left it to the NIH to set ethics guidelines determining which cell lines now will qualify for government funding.
Many scientists had hoped that the guidelines would allow use of stem cells derived from embryos created just for science, perhaps even those created using cloning techniques that could make them genetically customized for a potential recipient. Some existing stem-cell guidelines that are used in privately funded research -- including guidelines from the National Academy of Sciences -- are open to all types.
"We discussed the pros and cons of every conceivable variation on this policy," Kington said.
Ultimately, the NIH proposed limiting new grants to research that uses stem cells originally derived from fertility-clinic leftovers, the extra embryos that couples wind up not needing and thus often are thrown out.
That's in line with legislation passed by the last Congress but never signed by then-President George W. Bush.
"There's compelling broad support both in the scientific community and the public at large" for that approach, Kington said. "There is not similar broad support for using other sources at this time."
The guidelines also demand that the woman or couple who donate the original embryo give proper informed consent. There are other options for such donors, such as donating the embryo to another infertile woman, and all must be explained. The donation must be voluntary, without pressure from scientists.
And the guidelines also clearly forbid some types of research using human embryonic stem cells -- such as mixing them with embryos from monkeys and other primates.
The NIH will accept public comments on the guidelines for a month and assess those comments before issuing final rules by early July.
FOX News' Daniela Sicuranza and The Associated Press contributed to this report.