The US government Friday unveiled guidelines for publicly-funded embryonic stem cell research limiting it to embryos developed in test tubes for would-be parents but never used.
The draft guidelines, issued by the National Institutes of Health, came in response to President Barack Obama's executive order on March 9 lifting a ban on embryonic stem cell research.
"These draft guidelines would allow funding for research using human embryonic stem cells that were derived from embryos created by in vitro fertilization (IVF) for reproductive purposes and were no longer needed for that purpose," the NIH said.
"NIH funding for research using human embryonic stem cells derived from other sources, including somatic cell nuclear transfer, parthenogenesis, and/or IVP embryons created for research purposes, is not allowed under these guidelines," it said.
Such research could use the embryos developed in fertility clinics for couples but which were never used and would otherwise be destroyed.
Some religious groups oppose the destruction of any human embryo as the taking of a human life.
But in reversing the ban imposed by former president George W. Bush, Obama argued that the promise of medical breakthroughs through stem cell research could not go unexplored.
Such research could lead to advances in the treatment of diseases such as Parkinson's, diabetes and Alzheimer's, although Obama acknowledged that there were no guarantees.
Many researchers have been awaiting the NIH guidelines to design research projects that would be eligible for federal funding.
The NIH is giving the public 30 days to comment on the guidelines once they are formally published April 24.
The guidelines also sought to prevent the commercialization of embryonic stem cells, barring inducements to potential donors or that they not benefit financially if the research has commercial potential.