Supreme Court Justice John Paul Stevens yesterday blocked the enforcement of Illinois and Wisconsin laws that ban a type of late-term abortion, as the controversy over what opponents call "partial birth" abortion moved closer to an ultimate resolution at the high court.

The 7th U.S. Circuit Court of Appeals had upheld the late-term abortion bans in October and, after weeks of vacillating actions, refused yesterday to temporarily suspend the statutes pending appeals to the Supreme Court.

Stevens's short order in the cases, which were directed to him as the justice who oversees emergency business in the midwestern 7th Circuit, said that the laws would be halted until the Supreme Court acts on the appeals, which could take more than a year.

Bans on partial-birth abortion have become the focal point of today's abortion wars, roiling Congress, state legislatures and now the courts. While the 7th Circuit upheld the constitutionality of such laws in Wisconsin and Illinois, the 8th Circuit only a few weeks earlier had struck down similar bans in Arkansas, Iowa and Nebraska.

"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.

Those who have challenged the Wisconsin and Illinois bans contend that the statutes are vaguely written and could be interpreted to prevent women from undergoing procedures that the Supreme Court has ruled constitutional. The Wisconsin law calls for life in prison for anyone performing the late-term procedure except to save the mother's life, and physicians who are seeking to have that law suspended argue that they would have to worry about going to jail even for abortions that the Supreme Court might eventually allow.

It is difficult to predict what the justices will do with a given appeal, and most are rejected without explanation. But because lower courts are split on the constitutionality of partial-birth abortion laws, there is a good chance the justices will take up the issue. If they agree to hear the case, it will be the first time the justices will address a woman's right to end a pregnancy since 1992, when they narrowly upheld Roe v. Wade, the 1973 decision that made abortion legal nationwide.

The state of Nebraska has already appealed the 8th Circuit ruling to the high court. Appeals in the Wisconsin and Illinois cases are due in January. The court will likely decide this spring whether to take the appeals. Oral arguments would be scheduled for later in the year, with a probable ruling in 2001.

Indicative of the passions that swirl around the abortion issue, the 7th Circuit was bitterly divided in its discussions of whether to suspend the laws temporarily until the appeals could be resolved. The court twice refused to halt enforcement of the laws but then reconsidered. When it ultimately declined to suspend the laws yesterday, it was by a 5 to 5 vote.

The dissenting judges said the decision showed a "regrettable disregard for the importance of the issues." Judge Diane P. Wood wrote, "We are dealing, after all, with matters of life and death, as they relate to a woman's exercise of a constitutional right the Supreme Court has repeatedly recognized."