Frist, who last month said he did not at this time support expanded federal financing of such research, was to explain his decision to now support such financing in a speech on the Senate floor.
In excerpts from Frist's speech obtained by CBS News, the majority leader says "embryonic stem cells uniquely hold specific promise for some therapies and potential cures that adult stem cells cannot provide. I believe today … that the federal government should fund embryonic stem cell research."
The Tennessee Republican, who has been said to be eyeing a run for the GOP presidential nomination in 2008, said only stem cells from embryos destined "with absolute certainty to be discarded and destroyed" should be considered for research.
In 2001, President Bush announced his position on stem cell research, saying the government should pay only for research of stem cell colonies, or lines, that were created by that date where the "life or death" decision already has been made.
Frist, who also is a heart and lung transplant surgeon, credited Mr. Bush with opening the doors for federal funding of embryonic stem cell research, and said when this policy was announced, policy-makers thought 78 stem cell lines would be available. Since then, the number has dropped to 22.
"Now is the time to expand the president's policy because it's promising research, but it must be done in a way that is ethically considerate, that respects the dignity of human life," said Frist.
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.
The shift in views could impact Frist's presidential prospects since it would put him in conflict with not only the White House but also Christian conservatives, whose support he has been courting.
Almost two-thirds of Americans say they support embryonic stem cell research and a majority of people say they would like to see fewer restrictions on taxpayer funding for those studies, according to recent polls.