After years of emotional debate, Congress sent President Bush legislation to ban partial-birth abortion (search) — the most significant restriction since the landmark Supreme Court decision legalizing abortion three decades ago.

"This is an enormous day. It's been a long seven-year fight about the issue of partial-birth abortion," Sen. Sam Brownback (search), R-Kan, said of Tuesday's vote. He was a leader of the drive to end abortions, generally carried out in the second or third trimester, in which a fetus is partially delivered before being killed.

Bush, traveling in Asia, said in a statement, "This is very important legislation that will end an abhorrent practice and continue to build a culture of life in America."

Opponents of the bill also stressed its importance, for different reasons.

"This is indeed a historic day," said Sen. Barbara Boxer (search), D-Calif., lead opponent of the legislation, "because for the first time in history Congress is banning a medical procedure that is considered medically necessary by physicians."

Abortion rights groups promised to challenge the law in court as soon as Bush signed it.

Senate Majority Leader Bill Frist (search), R-Tenn. — a heart surgeon — told Fox News he's confident the ban will withstand any court challenges. Calling the procedure "egregious, outlandish and ghoulish," Frist argued it is not something that is medically necessary — as some Democrats have argued in the case of a woman's health — and said he is excited that the bill will finally be signed, rather than vetoed, by the president.

Sen. Tom Harkin, D-Iowa, warned that the abortion ban was a first step toward overturning the 1973 court ruling. "I see where this is going: a couple of votes here or there in the next election, you can kiss Roe v. Wade goodbye."

The 64-34 vote came three weeks after the House passed the same measure by 281-142.

Bush had urged Congress to pass the ban, which Republicans had pursued since the GOP captured the House in 1995, and the president had said he would sign it into law.

But opponents said the first federal ban on abortion since the Roe v. Wade decision was unconstitutional and, like similar state laws, would be struck down.

The president, said Sen. Frank Lautenberg, D-N.J. "will become the first United States president to criminalize a safe medical procedure." Doctors who violate the ban would be subject to prison terms of up to two years.

The legislation bans a procedure, generally performed in the second or third trimester, in which a fetus is partially delivered before a doctor punctures the skull.

However, the two sides differed widely on the frequency and definition of partial-birth abortion, which is not a formal medical term.

The 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."

Opponents of the legislation argued that, as defined in the bill, it could apply to several safe and common procedures, and that the real goal of the legislation was to erode overall abortion rights.

"I see what this is about ... this is about politics," said Boxer. "I never dreamed I'd be down here with senators who think they know more than doctors."

But Sen. Rick Santorum, R-Pa., chief sponsor of the bill, said the procedure was both inhumane and unnecessary. "We can't allow this kind of brutality to corrupt us. It makes a much more brutal and harsher country if we stand here and say, yes, for whatever reason, we are going to allow this to occur."

"This legislation we just passed will save lives ... potentially thousands of lives," Frist said.

But Democratic presidential candidate Howard Dean, who is also a doctor, said: "As a physician, I am outraged that the Senate has decided it is qualified to practice medicine." He said the legislation "will endanger the lives of countless women."

Several groups, including the National Abortion Federation and the Center for Reproductive Rights, plan to challenge the measure in court as soon as it is signed into law. "We will take this fight from the Capitol to the courtroom to safeguard the lives and health of women," said Vicki Saporta, president of the National Abortion Federation.

Planned Parenthood Federation of America President Gloria Feldt said her group would seek an injunction preventing the legislation from taking effect.

A key focus will be the Supreme Court's 5-4 ruling in 2000 that a similar Nebraska law was unconstitutional because the definition of the practice was too vague -- making it unclear to doctors what procedures were illegal -- and didn't have an exception concerning risks to the health of the mother to go along with an exception for when the life of the mother was in danger.

Santorum argued that supporters had met those constitutional questions by tightening the definition and offering extensive findings that the procedure was never needed to protect the health of the mother.

President Clinton twice vetoed partial-birth bills on the grounds that they did not include health exceptions.

Anti-abortion leaders said the coming court battle would have far-reaching ramifications.

"In 2000, five Supreme Court justices said that Roe v. Wade guaranteed the right of abortionists to perform partial-birth abortions whenever they see fit. But Congress is now inviting the Supreme Court to re-examine that extreme and inhumane decision," said Douglas Johnson, legislative director for the National Right to Life Committee.

The Associated Press contributed to this report.