In conjunction with the veto, Bush issued an executive order calling on federal agencies to strengthen the nation’s commitment to research on pluripotent stem cells.

Adult stem cells from a variety of sources, including bone marrow, the placenta and umbilical-cord blood, have led to successful treatments for a number of diseases. Adult stem cells are called pluripotent because they have the power to turn into many of the 200-plus types of differentiated cells found in the body.

Embryonic stem cells are called omnipotent because they can turn into any of those differentiated cells.

The vetoed bill was titled the Stem-Cell Research Enhancement Act of 2007. It passed in the Senate April 11 by a 63-34 vote and in the House June 7 by a vote of 247-176. Neither vote reflected the two-thirds majority that would be needed to override a veto.

The day before the House voted to relax the funding restrictions on human embryonic research, Cardinal Justin Rigali of Philadelphia, chairman of the U.S. bishops’ Committee on Pro-Life Activities, had urged it to defeat the bill. In a letter to all House members, he said, “Embryonic stem-cell research has been as disappointing in its results as it has been divisive to our society. Pursuit of this destructive research will almost certainly require you to embrace more and more egregious violations of moral norms in the effort to bring its ‘promise’ to fruition.

“Ethically sound research using non-embryonic stem cells has continued to advance, helping patients with over 70 conditions in clinical trials,” he added. “Since Congress debated this issue last summer, further evidence has emerged on the versatility of adult stem cells and on the ability of adult cells to be reprogrammed to rival the flexibility of embryonic cells.”

Democratic leadership had made the bill a top priority when the Democrats gained control of Congress this year. It would have ended the Bush administration’s six-year-old policy limiting federal funding of human embryonic stem-cell research to projects that relied only on colonies of embryonic stem cells created before Aug. 9, 2001, the date that policy was announced.

Democratic National Committee Chairman Howard Dean sharply criticized the veto, saying, “Bush once again put political posturing ahead of sound science, turning his back on the overwhelming majority of Americans who support stem-cell research and the 100 million Americans suffering from debilitating diseases who could benefit from this life-saving science.”

Sen. Hillary Rodham Clinton of New York, a contender for the Democratic presidential nomination next year, accused Bush of putting “ideology before science, politics before the needs of our families.”

White House press spokesman Tony Snow called the veto an attempt “to respect people’s conscience on such an issue.”

“The president does not believe it’s appropriate to put an end to human life for research purposes,” he said. “That’s a line he will not cross.”

In his veto message to the Senate, Bush said since 2001 his administration “has made more than $130 million available for research on stem-cell lines derived from embryos that had already been destroyed. We have also provided more than $3 billion for research on all forms of stem cells, including those from adult and other non-embryonic sources.”

The president’s new executive order directs the Department of Health and Human Services and the National Institutes of Health to ensure that any human pluripotent stem-cell lines produced in ways that do not create, destroy or harm human embryos will be eligible for federal funding. It expands the NIH’s Human Embryonic Stem Cell Registry to include all types of ethically produced human pluripotent stem cells as well, and renames the registry the Human Pluripotent Stem Cell Registry. It encourages scientists to work with the NIH to add ethically produced stem-cell lines to the registry.

An article appearing June 7 in Nature, an international science journal, reported that research by three separate teams showed that the skin cells of mice could be reprogrammed to become embryonic stem cells. The magazine said the “surprisingly straightforward” procedure could end the demand for the creation and destruction of embryos for the sake of obtaining such cells.

Richard Doerflinger, deputy director of the bishops’ Secretariat for Pro-Life Activities, said that “adult cell reprogramming does not pose the moral problem of creating or destroying (human) embryos.” The reported advances “would be a gain for science, ethics and society,” he said.