WASHINGTON (AP) – Pushing back against the Democratic-led Congress, President Bush vetoed a bill Wednesday that would have eased restraints on federally funded embryonic stem cell research.

Democrats, who had made the stem cell legislation a top priority when they took control of the House and Senate in January, were quick to denounce the president’s decision.

“This is just one example of how the president puts ideology before science, politics before the needs of our families, just one more example of how out of touch with reality he and his party have become,” Senator Clinton, Democrat of New York, told the Take Back America conference of liberal activists Wednesday.

To blunt criticism, the White House said Mr. Bush is issuing an executive order directing the Health and Human Services Department to promote research into cells that – like human embryonic stem cells – also hold the potential of regenerating into different types of cells that might be used to battle disease.

“This is, certainly not an attempt to muzzle science,” White House press secretary Tony Snow said. “It is an attempt, I think, to respect people’s conscience on such an issue.”

If the measure Bush vetoed would have become law, the White House said it would have compelled taxpayers for the first time in our history – to support the deliberate destruction of human embyros. Snow said Bush’s executive order will encourage scientists to work with the government to add research on new stem cell lines – that does not involve the creation, harming or destruction of human embryos – to the list of projects eligible for federal funding.

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

Senate Majority Leader Harry Reid is expected to schedule an override vote, but the date has not been set. Democrats, however, currently do not have enough votes to override Mr. Bush’s veto.

Scientists were first able to conduct research with embryonic stem cells in 1998, the NIH says. There were no federal funds for the work until Bush announced on Aug. 9, 2001, that his administration would make the funds available for lines of cells that already were in existence.

Currently, states and private organizations are permitted to fund embryonic stem cell research, but federal support is limited to cells that existed as of Aug. 9, 2001. The latest bill was aimed at lifting that restriction.

The science aside, the issue has weighty political and ethical implications.

Public opinion polls show strong support for the research, and it could return as an issue in the 2008 elections.

Opponents of the latest stem cell measure insisted that the use of embryonic stem cells was the wrong approach on moral grounds – and possibly not even the most promising one scientifically. These opponents, who applaud Bush’s veto, cite breakthroughs involving medical research conducted with adult stem cells, umbilical cord blood and amniotic fluid, none of which involve the destruction of a human embryo.

This was the third veto of Mr. Bush’s presidency. His first occurred last year when he rejected legislation to allow funding of additional lines of embryonic stem cells – a measure that passed over the objections of Republicans then in control. The second legislation he vetoed would have set timetables for U.S. troop withdrawals from Iraq.