WASHINGTON – The Supreme Court set the stage yesterday for a major ruling on abortion by agreeing to decide whether Congress can outlaw so-called “partial birth” abortions during the mid-term of a pregnancy.

The fate of the federal law, the first nationwide ban on an abortion procedure, probably depends on President Bush’s two new appointees: Chief Justice Roberts and Justice Alito.

The court has been closely split on how strictly the government may regulate abortion, with former Justice O’Connor usually casting a deciding vote.

Justice Alito, Justice O’Connor’s replacement, took his seat on the bench for the first time yesterday morning just as the court’s staff was issuing a list of new cases that will be heard in the fall. It included Gonzales v. Carhart, the Bush administration’s appeal of a lower court ruling which declared unconstitutional the Partial Birth Abortion Ban Act of 2003.

The legal dispute now turns on two questions. Can the government regulate abortion in a way that might endanger the health of some women? And whose opinion deserves greater weight in deciding whether this abortion procedure is needed – members of Congress or the medical experts who testified in court?

The court will hear arguments on the case in October. A ruling on the issue is not likely to deal directly with Roe v. Wade and the basic right of pregnant women to choose abortion. However, a victory for the Bush administration would signal the reconstituted court is more willing to regulate and restrict abortion.

In the past, Justice Kennedy has voted to uphold a state ban on partial birth abortions. Justices Roberts and Alito are also believed to be abortion opponents, and they could form a new majority upholding the federal ban.

Six years ago, the high court struck down a state ban on this abortion procedure in a Nebraska case, saying medical experts believed this way of performing abortions was safer for the mother because it reduced the risk of bleeding and infections. The decision came on a 5-4 vote, with Justice O’Connor in the majority.

Republican lawmakers then pushed through a federal ban that could send doctors to prison for two years. They said these abortions were gruesome and inhumane because they involved crushing the skull of the fetus as it is removed. Congress also said this abortion procedure was “never medically indicated.”

Appealing the ruling that the federal law was unconstitutional, U.S. Solicitor General Paul Clement, representing the Bush administration, said the Supreme Court should give “substantial deference … to Congress’s factual findings” that this abortion procedure was not needed.

On Tuesday, anti-abortion groups welcomed the court’s decision to revisit the issue. The American Center for Law and Justice said it was “hopeful the high court will put an end to this barbaric procedure.”

Supporters of abortion rights said they worried the court’s action is a signal of trouble ahead. Planned Parenthood called the decision to take up the case a “dangerous act of hostility” toward women.

During the 1990s, President Clinton vetoed a federal bill to outlaw such abortions, saying it posed a threat to the health of some women. When Congress passed the new measure three years ago, President Bush signed it, saying it would end a “terrible form of violence (that) has been directed against children who are inches from birth.”