Abortion rights advocates said they would immediately go to court to stop what they said was a dangerous incursion against the 1973 Supreme Court decision that legalized abortion.
The Senate voted 64-34 Tuesday to ban a type of abortion, generally carried out in the second or third trimester, in which a fetus is partially delivered before being killed. The House approved the legislation this month, and Mr. Bush has urged Congress to get it to his desk.
"This is very important legislation that will end an abhorrent practice and continue to build a culture of life in America," he said in a statement. "I look forward to signing it into law."
That signature would end a legislative crusade that began when Republicans captured the House in 1995. President Clinton twice vetoed similar bills, arguing that they lacked an exception to protect the health of the mother, and in the first year of the Bush administration a Democratic-controlled Senate stopped its advancement.
In the final Senate vote, 17 Democrats joined 47 Republicans to support the ban. Three Republicans voted against the legislation.
With the outcome never in doubt, at least three groups supporting abortion rights prepared lawsuits to stop the law from going into effect and to challenge its constitutionality.
Talcott Camp, an attorney for the American Civil Liberties Union, said the case could take two to three years to work its way through the courts. The ACLU will represent the National Abortion Federation in its lawsuit.
There was a wide divergence of views about what the procedure encompasses or how frequent it is used, but the opposing sides agreed the legislation was of major consequence.
"Today we have reached a significant victory as we continue to build a more compassionate society and a culture that values every human life," said Sen. Rick Santorum, a Pennsylvania Republican, the bill's sponsor.
Senate Majority Leader Bill Frist of Tennessee, a heart surgeon, said the ban could save the lives of thousands of soon-to-be-born babies.
"I can say without equivocation that partial birth abortion is brutal, it is barbaric, it is morally offensive, and it is outside the mainstream practice of medicine," he said.
Another physician-politician, Democratic presidential candidate Howard Dean, said it is the women who need the procedure whose lives were put at risk by Tuesday's Senate vote.
"As a physician, I am outraged that the Senate has decided it is qualified to practice medicine," said Dean, a former governor of Vermont. He said the legislation "will endanger the lives of countless women."
Other opponents decried a bill they said would criminalize a safe medical practice and subject doctors who violate it to up to two years in prison. The bill "for the first time in history bans a medical procedure without making any exception for the health of the woman," said Sen. Barbara Boxer, a California Democrat. "This is a radical, radical thing that is about to happen here."
Sen. Tom Harkin, an Iowa Democrat, said the bill was a clear threat to the future of Roe v. Wade, the 1973 Supreme Court decision that legalized abortion nationwide. "I say to the women of America: this is step one," Harkin said.
Neither the American College of Obstetricians and Gynecologists, nor the American Medical Association advocate the procedure, generally performed between the 18th and 24th weeks of pregnancy.
The AMA even states that "except in extraordinary circumstances, maternal health factors which demand termination of the pregnancy can be accommodated without sacrifice of the fetus," CBS News Correspondent Elizabeth Kaledin reports.
But doctors like Paul Blumenthal say combining the words "never" and "late-term abortions" is risky. Though difficult to foresee and outline, any number of complications can arise during a pregnancy. By outlawing even one option, no matter how rarely used, ethicists believe congress is treading on dangerous ground.
"There are situations in which we may have no choice but to provide a procedure that this bill will declare illegal," Blumenthal said.
Key to the court battle will be a 5-4 Supreme Court ruling in 2000 that a similar Nebraska state law was unconstitutional because the definition of "partial birth" was too vague and left doctors unsure of what practices were illegal. The court also found fault with the legislation because, while it provided an exception when the life of the mother was in danger, there were no protections for a woman's health.
The new bill defines partial birth abortion as delivery of a fetus "until, in the case of a headfirst presentation, the entire fetal head is outside the body of the mother, or, in the case of the breech presentation, any part of the fetal trunk past the navel is outside the body of the mother for the purpose of performing an overt act that the person knows will kill the partially delivered living fetus."
Santorum argued that supporters had met the constitutional questions by tightening the definition and offering extensive findings that the procedure was never needed to protect the health of the mother.
But the president of the Planned Parenthood Federation of America, Gloria Feldt, said the bill remained unconstitutional because it "prevents women, in consultation with their families and trusted doctors, from making decisions about their own health."
Tony Perkins, president of the anti-abortion Family Research Council, urged Attorney General John Ashcroft to put up a stiff legal defense. "Given an activist judiciary, the prospects for the ban surviving a court challenge are dim unless the attorney general is ready to pour resources and energy into the fight to defend it," he said.
The vast majority of abortions occur relatively early in pregnancy. According to the Centers for Disease Control and Prevention, roughly 58 percent of abortions take place before the end of the eighth week of gestation. Eighty-eight percent take place by the end of the 12th week.