WASHINGTON - The Supreme Court dramatically limited states' power to ban so-called partial-birth abortions Wednesday, a 5-4 ruling that immediately escalated the bitter, decades-old debate over women's right to end their pregnancies.
Closing out its 1999-2000 term with some of the most divisive rulings in years, the court struck down Nebraska's partial-birth abortion law as an ''undue burden'' on women's rights.
Thirty other states have similar laws, but the justices disagreed on just how their ruling ultimately will affect those other laws. More litigation seemed certain.
James Bopp, a lawyer for the National Right to Life Committee, called the decision ''a radical expansion of the abortion right.'' Clarke Forsythe of Americans United for Life added: ''It's the most extreme decision on abortion ever issued by the Supreme Court.''
The court first legalized abortion nationwide in its famous Roe v. Wade ruling, the 1973 landmark based on women's constitutional rights.
Those rights were upheld in 1992 by a 6-3 vote, the court's last major ruling on abortion. Nothing in Wednesday's decision suggested the court's vote split on the core abortion issue had changed.
Abortion-rights advocates expressed more relief than joy.
Janet Benshoof, whose Center for Reproductive Law and Policy represented the Nebraska doctor who challenged his state's law, said the close vote ''demonstrates that the right to choose is a fragile one.''
Planned Parenthood added: ''While it looks like a victory, this is a beginning - not the end. Anti-choice state legislatures and governors across the country will use this ruling as a blueprint for drafting new bans on abortion procedures.''
President Clinton issued a statement at the White House pledging to veto any similar legislation that widely restricts late-term abortions. ''A woman's right to choose must include the right to choose a medical procedure that will not endanger her life or health,'' Clinton said. ''Today's decision recognizes this principle and marks an important victory for a woman's freedom of choice.''
In other decisions, the court said:
-Gave states greater leeway to restrict anti-abortion demonstrators outside clinics. The ruling upheld a Colorado limit on ''sidewalk counseling.''
-The Boy Scouts can ban homosexuals from serving as troop leaders. By extension, the ruling in a New Jersey case could let the Scouts exclude as well young boys who say they are gay.
-Significantly lowered the figurative wall of separation between church and state by ruling in a Louisiana case that taxpayer money can be used to buy computers and other instructional materials for religious schools.
The emotional abortion issue already had become entwined with this year's presidential election because Republican George W. Bush supports bans on partial-birth abortions and Democrat Al Gore opposes them.
President Clinton said the nation's next president is likely to replace two to four Supreme Court justices. ''Depending on who they are,'' he said, abortion rights are ''very much in the balance.''
The Republican-led Congress is working out final details of a bill that would ban the surgical procedure. President Clinton has vetoed two such bills.
Partial-birth abortion is not a medical term. Doctors call the method dilation and extraction, or D&X, because it involves partially extracting a fetus, legs first, through the birth canal, cutting the skull and draining its contents.
A more common procedure is dilation and evacuation, or D&E, in which an arm or leg of a live fetus may be pulled into the birth canal during the abortion operation.
The court said the Nebraska law, while purportedly aimed only at the D&X method, could criminalize the D&E method as well.
The law's other big flaw, Justice Stephen G. Breyer wrote for the court, was that it lacked an exemption that would allow the D&X procedure if it a doctor concluded it was the best way to preserve a woman's health.
Joining Breyer were Justices John Paul Stevens, Sandra Day O'Connor, David H. Souter and Ruth Bader Ginsburg.
O'Connor, who supplied the critical fifth vote, suggested in a concurring opinion that states can ban some partial-birth abortions.
''A ban on partial-birth abortion that only proscribed the D&X method of abortion and that included an exception to preserve the life and health of the mother would be constitutional in my view,'' she said.
Forsythe, the anti-abortion advocate, called O'Connor's words ''an illusion, a national hoax.''
The court's dissenters - Chief Justice William H. Rehnquist and Justices Antonin Scalia, Anthony M. Kennedy and Clarence Thomas - appeared to agree that the 30 other states may not be able to come up with easy remedies.
Writing for himself, Rehnquist and Scalia, Thomas said, ''Today we are told (by the majority) that 30 states are prohibited from banning one rarely used form of abortion that they believe to border on infanticide.''
And Kennedy, a co-author of the 1992 ruling that upheld abortion rights, wrote in a dissenting opinion: ''Justice O'Connor assures the people of Nebraska they are free to redraft the law.... The assurance is meaningless.''
Ginsburg and Breyer joined the court after the 1992 decision. Wednesday's ruling was their first on abortion.
The procedure at issue in the Nebraska case is used for some abortions close to the point of viability, when a fetus is able to live outside the uterus. Past abortion rulings make clear that states can take numerous steps to protect fetal life once viability occurs, generally around the sixth month of pregnancy.
Nebraska's law, along with those in Arkansas and Iowa, was invalidated by a federal appeals court last year. But another federal appeals court upheld partial-birth abortion bans in Wisconsin and Illinois.
An appeal of that federal appeals court ruling still is pending before the justices, and likely will be set aside and sent back for more study when the court's clerk issues new orders from the justices Thursday.
The state's 1997 law was challenged by Dr. Leroy Carhart, one of only three doctors in Nebraska known to perform abortions.
Carhart sat quietly in the ornate courtroom Wednesday and showed little emotion as the decision was summarized from the bench. Later, he said, ''This is a victory for all Americans who believe that the government must not be allowed to meddle in the private decisions best left to women, their families and their doctors.,''
On the Net: For the decision in Stenberg v. Carhart: http://supct.law.cornell.edu/supct/html/99-830.ZS.html