WASHINGTON - President Bush, facing congressional efforts to loosen his administration's strict limits on embryonic stem cell research, vowed yesterday to veto legislation that would allow federal funds to be spent experimenting with cells from donated frozen embryos.
Bush said he wouldn't condone "the use of federal money, taxpayers' money, to promote science which destroys life in order to save life." Speaking to reporters in the Oval Office, Bush added, "If the bill does that, I will veto it."
His comments set up a confrontation with the Republican-led Congress. Bipartisan efforts to relax Bush's stem-cell policy have attracted enough support, including among conservatives who oppose abortion rights, to force a vote on the matter in the House next week.
A coalition of Republicans and Democrats is likely to push through a measure Tuesday that would allow federal money to be spent for research on stem cells derived from frozen embryos created for fertility treatments, and donated by couples who no longer plan to use them.
Similar legislation has a good chance of passing the Senate, but it's not clear whether proponents in either chamber would have enough backing to override a presidential veto.
Bush's carefully calibrated stem cell policy - announced during his first televised address - blocks federal funding for research on new embryonic stem cells, allowing taxpayer money to go only to experiments with stem cell lines existing before the Aug. 9, 2001, statement.
With his veto threat yesterday, Bush made it clear he does not intend to back down, even though that stance is creating bitter fissures among Republicans and is at odds with a sweep of public opinion in favor of expanded research.
Bush also expressed concern about reports this week that scientists in South Korea, through government-funded research, have cloned human embryos and extracted stem cells.
"I worry about a world in which cloning becomes acceptable," Bush said in answer to a question about that report.
Trent Duffy, a White House spokesman, said the South Korean developments on cloning, which he said the president is "dead-set against," highlight the need to tread carefully in the pursuit of scientific discovery.
Opposition to Bush's policy has picked up momentum with the help of prominent advocates, including Nancy Reagan, whose support for expanded embryonic stem cell research was rooted in her husband's battle with Alzheimer's disease.
And abortion opponents increasingly argue that backing some stem cell experimentation is a pro-life position.
"I do believe very strongly that it is possible to be both anti-abortion and pro-embryonic stem cell research," Sen. Orrin G. Hatch, a Utah Republican who is sponsoring a measure to relax Bush's restrictions, said earlier this month. "I believe being pro-life means caring for the living as well."
Republicans and Democrats who are pushing to revise Bush's stem cell policy - backed by a large group of patient groups, scientists, medical organizations and research universities such as Johns Hopkins - contend that using stem cells from embryos that would otherwise be discarded is in keeping with Bush's principle of refraining from creating life for the specific purpose of ending it.
The measure slated for House action next week "draws a strict ethical line," said Rep. Michael N. Castle, the Delaware Republican who is sponsoring it along with Democratic Rep. Diana DeGette of Colorado. "The bottom line is, when a couple has decided to discard their excess embryos, they are either going to be discarded as medical waste or they can be donated for research. Let's uncover the promise of stem cell research in the hope of helping the millions of Americans who are suffering."
Advocates regard stem cells from embryos as an exceptionally promising area of research that might ultimately help treat or cure a wide variety of crippling illnesses, including Alzheimer's, Parkinson's and juvenile diabetes, as well as spinal cord injuries. Embryonic stem cells are particularly prized by researchers for their potential to develop into all sorts of cells and tissues.
But because an embryo must be destroyed for the cells to be extracted, the research sparks ardent opposition from religious conservatives, who say it requires the taking of life. The embryos could be adopted rather than discarded, they argue.
"This is a logic that a society would never adopt with other people who are facing short life-spans: 'They're going to die anyway, so it doesn't matter what we do with them,' " said Douglas Johnson, the legislative director of the National Right to Life Committee.
Rep. Christopher H. Smith, a New Jersey Republican who is a chair of the Pro-Life Caucus, is working to sap support from Castle's measure. He is pushing his own bill - also expected to win House approval next week - that would create a national umbilical cord blood bank and encourage research on stem cells taken from cord blood.
"Our cord blood effort, and adult stem cells as well, remain the best-kept secret in America," Smith said yesterday, saying that such material has led to breakthroughs on treating sickle cell anemia and certain forms of cancer. He argued that it has just as much potential as embryonic stem cells.
Bush reiterated yesterday that he's a "strong supporter of adult stem cell research," which is unrestricted under his policy.
Many scientists believe adult stem cells have far less potential than those drawn from embryos, because they have less capacity to develop into different types of cells, although recent research has shown they might have the ability to do so.
Ole Isacson, a stem cell researcher at Harvard University, said Bush's restrictions on embryonic stem cell work had slowed the pace of research in the United States.
"It has not been irreversibly harmed yet. But the restrictions are not allowing us to accelerate the search for new therapies," said Isacson, who is trying to use stem cells to find new treatments for Parkinson's.
"The policy has set us back," said Leonard Zon, another Harvard researcher. "South Korea is now doing work that many people thought the U.S. should do."
Other scientists expressed disappointment over Bush's criticism of South Korea.
"It is frustrating ...," said Dr. John Gearhart, a pioneering stem cell researcher at the Johns Hopkins University. "Every time you see progress in the field, the comments are always the same: negative."
Gearhart said that the South Korean results showed the enormous potential of stem cell research and that it is so promising that it will inevitably move forward.
Sun staff writer Susan Baer contributed to this article.