WASHINGTON —  Chances for a Senate vote soon on stem cell research (search) grew uncertain Tuesday as the sponsors of a half-dozen bills haggled with each other and Majority Leader Bill Frist (search) over which should come up for debate.

Asked whether the bill was stuck or even dead for the year, Frist, R-Tenn., said, "Not yet."

President Bush has promised to exercise his first veto if the Senate approves the same bill the House passed in May overturning his restrictions on federal funding of medical research using stem cells from destroyed embryos.

Frist, balancing the interests of the White House, Senate Republicans and his own presidential ambitions, wants to require that any stem cell bill get 60 votes instead of the normally required simple majority — 51 if every senator votes. That could preclude the House bill or any of the Senate bills reaching the White House.

"Sen. Frist is riding three horses in this circus," observed one sponsor, Sen. Gordon Smith (search), R-Ore., who favors the House-passed bill. "Neither side wants the other to pass anything."

Judiciary Committee Chairman Arlen Specter (search), R-Pa., a Senate sponsor of the House-passed bill, said the matter can't be resolved without sponsors of various alternatives sitting down to work out their differences. Such a meeting had been scheduled for Monday night in Specter's office, but it never happened, according to two congressional sources. They spoke on condition of anonymity because they had not been authorized to discuss the matter publicly.

Further dimming the prospects for a stem cell vote Tuesday was Bush's Supreme Court nomination. The nominee must be confirmed by the Senate, which puts it atop the agendas of both Frist and Specter.

Specter and Sen. Tom Harkin, D-Iowa, had announced months ago that their bill mirroring the House's version had more than 60 votes to pass. Smith, however, said Tuesday he counts only 54 votes if a competing measure also is debated on the Senate floor.

Because harvesting embryonic stem cells destroys embryos, Bush and many other conservatives equate the process with abortion and view it as immoral. Proponents say the promise that stem cell research holds for treating and curing diseases such as Parkinson's and Alzheimer's outweigh the ethical concerns.

One alternative that Frist says is "similar in intent" to the House bill would make more stem cell lines available for research by qualifying for federal funding those taken from embryos after Bush's 2001 ban until whatever date he signs the bill into law.