Washington ? Senate supporters of embryonic stem cell research refused to take another no for an answer Tuesday, advancing politically popular legislation that is assured of passage, yet doomed for the second straight year to a veto that Congress cannot override.

“This bill eventually will become law,” vowed Sen. Dianne Feinstein, D-Calif., as debate opened on a bill to loosen federal funding restrictions on research that supporters say offers hope for treatment of numerous diseases.

“If not this year, then next year. If not next year, then the following year.”

Assuredly not this year.

President Bush, who cast the only veto of his tenure on a stem cell bill in 2006, quickly made it clear this year will be no different. The bill “would use federal taxpayer dollars to support and encourage the destruction of human life for research,” the White House said in a written statement.

Stem cells are created in the first days after conception, and are typically culled from frozen embryos, which are destroyed in the process.

The legislation would overturn a policy Bush established in 2001, when he said federal funds may only be used for research on a limited number of stem cell lines that were in existence before the day of his announcement. The administration’s goal was to satisfy calls for funding of scientific research without offending anti-abortion conservatives who had helped elect him to the White House.

The bill’s supporters concede they are short of the votes needed to override a veto, but they appeared eager to confront the president again on an issue with strong public backing.

“If we did everything based on veto threats by the president, we would never get anything done around here,” said Jim Manley, a spokesman for Senate Majority Leader Harry Reid of Nevada.

The result was a heavily political debate.

Last year’s veto was “another despicable example of science taking a back seat to politics in this administration,” said Sen. Edward M. Kennedy, D-Mass. “Policies that should rest on science are decided instead by crass political calculations of what is needed to appease the most intransigent elements of the Republican base.”

Republican opponents backed an alternative they said offered hope for scientific progress without destroying human embryos, a sticking point for conservatives.

“It’s a way around the culture wars,” added Sen. Norm Coleman of Minnesota, referring to the political battles that have raged in recent years on all issues touching on abortion. “It’s not all we want but it moves the science forward.”

Senate supporters of the veto-threatened bill said they would vote for the alternative, although they deemed it insufficient. Its prospects for House passage were uncertain.

Supporters of embryonic stem cell research say it alone promises treatment if not cures for a wide range of diseases.

Public opinion polls show support for the research is strong, 61 percent in an ABC/ Washington Post Poll earlier this year. In an AP-Ipsos poll last December, 56 percent of those polled said restrictions should be loosened, and Dr. Elias Zerhouni, whom Bush appointed as head of the National Institutes of Health, has called for the policy to be changed.

The issue also played a role in the 2006 midterm elections in which Democrats won control of both houses of Congress. The House approved its bill in January, although by a smaller margin than needed to override the threatened veto.