Capping two days of debate, the Senate also voted 70-28 to pass a separate measure backed by Republicans. It supported research in adult stem cells.

Bush said this legislation builds on "ethically appropriate research" and he urged Congress to pass the measure "so stem cell science can progress, without ethical and cultural conflict."

The Senate's action was the latest act in a drama that blends science and politics on an issue that affects millions of disease sufferers and their families.

"It's extremely frustrating to go through this Kabuki dance a second time with the president," said Peter Kiernan, head of the Christopher and Dana Reeve Foundation, which funds research.

"The one thing we know is we will outlast him."

Stem cells are created in the first days after conception. They are typically culled from frozen embryos, which are destroyed in the process. According to the National Institutes of Health Web site, scientists have been able to conduct experiments with embryonic stem cells only since 1998.

The embryonic stem cells have the ability to transform into a "dazzling array of specialized cells," the Web site says _ the property that scientists and others say offers the potential for the development of treatment for diseases as varied as juvenile diabetes, Parkinson's and Alzheimer's.

There was no federal money for the work until Bush announced on Aug. 9, 2001, that his administration would make it available for lines of stem cells that were in existence. Elected with the strong support of abortion foes and other conservatives, he said at the time his decision was designed to balance concerns about "protecting life and improving life."

He also limited the funds to cell lines derived from embryos that were surplus at fertility clinics, and that had been donated from adults who had given informed consent.

Advocates of the veto-threatened legislation argue that the number of stem cell lines available for research is smaller than needed, and that some of the material has become contaminated over time by mouse embryonic skin cells that typically are placed at the bottom of culture dishes used in the research.

The bill would permit funding for research on embryonic stem cells regardless of the date of their creation, so long as they were donated from in-vitro fertilization clinics, they would "otherwise be discarded" and donors gave their approval.

Bush cast the only veto of his presidency on a stem cell bill last year, but public support for the research is strong, and Democrats sought to use that to their advantage in the 2006 election campaigns.

Missouri became a testing ground, McCaskill challenging GOP  Sen. Jim Talent, who opposed expanded federally funded research. Michael J. Fox appeared in a television ad advocating greater research, and the visual image was arresting _ the 45-year-old actor swaying from his Parkinson's disease.

With federal funding limited, several states and private institutions have moved into the void.

California, New York and New Jersey have programs. Gov. Deval Patrick of Massachusetts recently announced he hoped to overturn restrictions left in place by his Republican  predecessor.

"We in Massachusetts increasingly see this as a competitive issue," said Dr. George Daley of Children's Hospital and the Harvard Stem Cell Institute. He said private institutions compete to hire promising scientists drawn to the field.

"I would say it's revolutionized biomedical research," he said. Rebutting claims by critics, he said, "You can't expect a cell which burst on the scene only as recently as 1998 to have found its way into patients yet. I don't know of any biological technology that translates into patients that soon."

But Carrie Gordon Earll, bioethics analyst at Focus on the Family, said that apart from the issue of embryo destruction, the inevitable result of the contested legislation would be to reduce funding available for adult stem cell work, which she said is more advanced.

"To our knowledge there are no clinical trials with human embryonic stem cells under way and there are 1,300 adult stem cell trials," she said, adding, "The destruction of embryos is not necessary for the advancement of regenerative research," she added.