"It's not just a matter of faith, it's a matter of science," Frist, R-Tenn., said on the floor of the Senate.
Frist's announcement immediately dented his support among Christian conservatives.
"Sen. Frist should not expect support and endorsement from the pro-life community if he votes for embryonic research funding," the Christian Defense Coalition said in a statement as Frist finished his speech.
"Senator Frist cannot have it both ways. He cannot be pro-life and pro-embryonic stem cell funding," said Rev. Patrick J. Mahoney, director of the group. "Nor can he turn around and expect widespread endorsement from the pro-life community if he should decide to run for president in 2008."
CBS News Political Editor Dotty Lynch reports that Tony Perkins, the President of the Family Research Council blasted Frist for "capitualting to the bio-tech industry" and called his announcement " very disappointing."
Earlier this year, Frist appeared to be courting these groups who carry a lot of weight in Republican primaries and caucuses, Lynch reports. He supported the decision to keep providing nourishment to Terry Schiavo and stood with the Christian conservatives on judicial nominations. He also appeared on videotape at the much touted "Justice Sunday" rally at wich organizers denounced Democrats as ''against people of faith'' for blocking judicial nominees.
The announcement drew praise from perhaps the most powerful advocate for the reasearch, former first lady Nancy Reagan.
"I was heartened by Senator Frist's support," she said in a statement. "Embryonic stem cell research has the potential to alleviate so much suffering. Surely, by working together we can harness its life-giving potential. Thank you, Dr. Frist, for standing up for America's patients." The late former President Ronald Reagan suffered from Alzheimer's disease.
Lynch added that a group supporting embryonic stem cell resarch has announced it will pull a TV ad in the early primary state of New Hamshire which attacked Frist for delay tactics on the stem cell bill. Stem Cell PAC began running the ad on Thursday night and today said it would take it down.
"As stem cell activists, and indeed as Americans, we need to thank Dr. Frist - and we need to work even harder to call upon other members of Congress and the President to join Dr. Frist and the overwhelming majority of Americans who support stem cell research, and the hope it offers," said John Hlinko the group's spokesman.
A heart-lung transplant surgeon who opposes abortion, Frist said loosening Mr. Bush's strict limitations on stem cell research would lead to scientific advances and "bridge the moral and ethical differences" that have made the issue politically charged.
"While human embryonic stem cell research is still at a very early stage, the limitation put into place in 2001 will, over time, slow our ability to bring potential new treatments for certain diseases," the Tennessee lawmaker said in his speech.
"Therefore, I believe the president's policy should be modified. We should expand federal funding ... and current guidelines governing stem cell research, carefully and thoughtfully, staying within ethical bounds," he said.
Mr. Bush has threatened to veto legislation for expanded financial support for stem cell research. A bill to finance more stem cell research has passed the House, but has been stalled in the Senate. Frist's support could push it closer to passage and set up a confrontation with Mr. Bush.
Frist's announcement will put pressure on the White House, predicted Sen. Arlen Specter, R-Pa., a cancer patient and the bill's sponsor.
"I know that the president will listen to what Sen. Frist has had to say," Specter said. "I'm not saying he is going to agree with it but ... I think may bring us all together on this issue."
It also could impact Frist's own political future. A likely presidential candidate in 2008, Frist has been courting religious conservatives who helped make Mr. Bush a twice-elected president and generally consider embryonic stem cell research a moral equivalent to abortion. But the announcement, coming just a month after Frist said he did not support expanded financing "at this juncture," could help him with centrist voters.
With those political realities in mind, Frist argued that his positions on stem cell research and abortion were not inconsistent. He said the decision was about policy, not politics.
Frist's decision brought quick praise from leading Democrats.
"It is a decision that will bring hope to millions of Americans," said Senate Democratic leader Harry Reid of Nevada. "I know there's still a long ways to go with the legislation, but a large step has been taken by the majority leader today ... and I admire the majority leader for doing it."
Said Sen. Edward M. Kennedy, D-Mass.: "As a physician, Sen. Frist has a moral calling to save lives and alleviate suffering. He honors his Hippocratic Oath today by recognizing the unique healing power of embryonic stem cells."