A federal appeals court in Chicago yesterday upheld bans on late-term abortions in Wisconsin and Illinois, opening the way for a confrontation at the Supreme Court over the constitutionality of a controversial but proliferating type of abortion law.

The 5 to 4 ruling contrasts with a decision last month by another federal appeals court that invalidated similar laws in three other states.

If the conflicting rulings reach the Supreme Court, it would mark the first time in seven years that the nation's highest court addressed a woman's right to end a pregnancy. Given how narrowly divided the justices are likely to be on the subject and the enduring emotional furor that surrounds the abortion debate, yesterday's decision is likely to have great repercussions, including in the 2000 elections.

The U.S. Court of Appeals for the 7th Circuit concluded yesterday that laws in Wisconsin and Illinois are constitutional, but it temporarily suspended their enforcement until lower courts could determine whether the ban on what opponents call "partial birth" abortion might unfairly restrict other abortion procedures protected by prior Supreme Court decisions.

"We conclude that both laws can be applied in a constitutional manner," said Judge Frank Easterbrook, writing for the majority. He said lower courts should review individual situations to ensure that women are not being denied constitutionally protected abortions. He said the laws do not violate a woman's right of privacy, nor are they an undue burden on a woman.

Richard Posner, chief judge of the 7th Circuit, who wrote for the minority, said the laws lack guidance for women seeking abortions and physicians who would perform them. "It is extremely difficult, indeed probably impossible, to distinguish a 'partial birth' abortion from the methods of abortion that are conceded to be privileged."

Advocates on both sides of the battle were swift to respond to the decision, which could lead to a Supreme Court review of the 1973 Roe v. Wade decision that first held that the Constitution protects a woman's right to abortion.

"If the Supreme Court adopts the Easterbrook majority opinion, it's the death knell for Roe v. Wade," said Janet Benshoof, president of the New York-based Center for Reproductive Law and Policy. "This ruling disregards a woman's health, a doctor's practice and the Constitution." She said the 7th Circuit specifically breached Supreme Court decisions by putting a fetus's health above a woman's at every stage of pregnancy.

But the National Right to Life Committee hailed the decision. "This makes it likely that the Supreme Court will rule . . . on whether Roe v. Wade covers pulling most of a living baby feet-first outside of the womb," NRLC Legislative Director Douglas Johnson said in a statement.

The Roe v. Wade decision set off a national debate that hasn't waned over the decades. Just seven years ago, amid continuing political and social fallout, the Supreme Court affirmed by a 5 to 4 vote that a woman has a constitutional right to end a pregnancy.

Since then, the battle over the conditions under which a woman may obtain an abortion has shifted to the nation's statehouses and to Congress. Last week, the Senate voted 63 to 34 for a national ban on "partial birth" abortion. The House is expected to take up the issue next year.

About 30 states have adopted laws banning the late-term abortion procedure. "Dilation and extraction," as the procedure is known medically, involves dilating a pregnant woman's cervix to allow the fetus to partially emerge, after which the fetus is killed by inserting a suction tube into its skull and removing the contents.

Not until last month's ruling from the 8th Circuit had any federal appeals court considered the merits of constitutional challenges to these late-term abortions. The 8th Circuit's ruling invalidated abortion laws in Arkansas, Iowa and Nebraska, saying they were written so broadly that they potentially covered all abortions.

The 1998 Wisconsin law calls for life in prison for anyone performing the procedure except to save the mother's life. It was upheld on June 4 by U.S. District Judge John C. Shabaz, but an appeals panel temporarily blocked its enforcement. The Illinois law was enacted in 1997, and a federal judge last year declared it unconstitutional.

Most of the 30 state laws have been blocked while challenges are underway. In Virginia, a permanent injunction against the state ban has been stayed, pending a ruling on the ban by the 4th Circuit Court of Appeals.