WASHINGTON (AP) _ An emotional Senate braced for a showdown over competing bills restricting late-term abortions. The leading sponsor of the Republican measure predicted his side would defeat a Democratic alternative.

However, Sen. Rick Santorum, R-Pa., acknowledged that the Democratic bill, which has White House support, was hampering efforts to build a veto-proof majority for his bill.

Santorum is pushing a House-passed GOP measure to ban use of a procedure opponents call ``partial-birth'' abortion except when a woman's life is in danger. Senate Minority Leader Tom Daschle, D-S.D., has countered with a bill that would ban some abortions after the point at which a fetus can live outside the womb.

Daschle's bill permits the late-term abortions when continuing the pregnancy would endanger a woman's life or cause ``grievous injury'' to her physical health. It also would not pre-empt laws already on the books in 41 states.

Daschle said he believes the number of senators willing to vote for his proposal, scheduled for a vote today, is ``in the 40s.''

He said today that it would ``offer a totally different approach ... to a repulsive practice that ought to be stopped.''

Sen. Mary Landrieu, D-La., a cosponsor, said Daschle's proposal would do ``something that's real, something that's right, something that's constitutional and something that's meaningful.''

The Senate was to vote first on another alternative by California Democratic Sens. Dianne Feinstein and Barbara Boxer that includes a broader health exception than Daschle's proposal. Their bill would allow late-term abortions to prevent the mother's death or ``avert serious adverse health consequences.''

Feinstein said Santorum's bill is a ``Trojan horse ... not at all what it seems to be on the outside. If you look on the inside, you will see that this bill is the first major legislative thrust to make abortion in the United States of America illegal.''

A final Senate vote could come today or perhaps next week. The GOP measure is identical to a bill President Clinton vetoed last year. Congress was unable to overturn the president's veto.

Clinton, who has promised another veto of the Republican bill if it passes, came out in support of Daschle's proposal Wednesday.

During impassioned debate, Santorum raised his voice and his face appeared flushed at times as he urged colleagues to support his effort to ban ``partial-birth'' abortions.

Using illustrations that showed a fetus in various stages of delivery, he said a physician performing a ``partial-birth'' abortion ``suctions the brains out of the baby. That causes the head to collapse and then the baby is delivered,'' he said. ``This is what we're trying to ban here, nothing else. Nothing else.''

The procedure, more complicated than first-trimester abortions, involves partially extracting a fetus, legs first, cutting an incision in the barely visible skull base and then draining the contents of the skull so it will fit through the birth canal.

The American Medical Association's board of trustees Wednesday said the procedure should be used rarely if at all, but did not take a position on the legislation. It said the procedure should be used if ``alternative procedures pose materially greater risk to the woman.'' The AMA's House of Delegates will consider making the report official policy at its annual meeting next month.

Abortion foes argue that a baby can be delivered prematurely and allowed to live when continuing the pregnancy would risk a woman's life or health.

Abortion advocates say such decisions should be made by women, their doctors, their families and their consciences _ not lawmakers.

``What this bill is really about is outlawing one procedure and then they'll go after the next procedure and then they'll go after the next and the next,'' Boxer said.

But Sen. Michael Enzi, R-Wyo., who plans to vote for Santorum's bill, said his prematurely born daughter's struggle to live taught him about the ``miracle of life.'' Now 25, Amy is deaf as a result of her birth three months early, but teaches English at a Wyoming middle school.

``Life is such a miracle that we've got to respect it and work for it every single day in every way that we can,'' added Enzi, a new member of the Senate. ``I think that this bill will help in that effort.''