President Bush's decision to permit federal funds to be used for limited embryonic stem cell research continues to generate controversy. Some scientists say the limits may be too strict. Bush administration officials say the president's decision is firm.
Supporters of stem cell research say it holds the promise of cures and treatments for debilitating diseases and injuries. Opponents say destroying embryos to extract their cells amounts to murder.
Mr. Bush says he took all these views into account in making what may prove to be one of the most important decisions of his presidency. He said no more embryos would be destroyed to provide cells for government-funded research. But he said Washington would pay for research using stem cells already extracted prior to his announcement.
The National Institutes of Health, the government's medical research facility, says there are about 60 or so stem cell lines available. A line is, in essence, a colony of stem cells grown from an embryo in the earliest stages of development. Unlike other cells in the body, stem cells do not have a specific function and can theoretically grow into any type of cell or tissue.
During a nationally broadcast interview, the President's Secretary of Health and Human Services said Mr. Bush will not permit the destruction of more embryos, even if there are signs of scientific breakthroughs.
Speaking on NBC's Meet the Press, Tommy Thompson said the president would stand by his decision.
"Are we going to allow the research to continue? 'Yes,' the president says. Are we going to allow for further derivation? No," said Mr. Thompson.
But scientists say the White House should be flexible. Dr. John Gearhart is conducting research at Johns Hopkins University. He appeared on the CBS news program Face the Nation. "We know that these stem cell lines, even though they have unlimited growth potential, we know there is a shelf life to these," he said. "And we are very concerned when we will need more lines, what happens then? And I think it will be sooner rather than later."
Congress will have its say starting in September when lawmakers take up legislation funding the National Institutes of Health. Some lawmakers say they will try to push legislation providing money for broader stem cell research.
But there is strong opposition from conservatives. Republican Congressman Chris Smith of New Jersey said on NBC's Meet the Press that any research involving cells from destroyed embryos - even those left over from fertility treatments - is wrong.
"We have got to change the idea that somehow there are excess or spare or throwaway embryos," he said.
But there is another view in the House - a unique one held by a Democrat from the small state of Rhode Island. Congressman Jim Langevin is paralyzed from the neck down, the result of a shooting accident when he was 16 years old. He too appeared on Meet the Press.
"Certainly stem cell research does offer great hope for finding a cure for spinal cord injuries." he said. "But this is not just about me or people with spinal cord injuries. It goes far beyond that. It could affect the one million children with juvenile diabetes, the four million people with Alzheimer's disease, or the one million people with Parkinson's disease."
Congress is expected to adjourn in October, leaving little time for in-depth consideration of the stem cell issue. But hearings are already being planned, and stem cell research is likely to have a place on the congressional agenda for many legislative sessions to come.