WASHINGTON — The graphic details of a disputed abortion procedure filled the Supreme Court yesterday as justices voiced concern with a federal ban on that operation.

Justices brought up uncomfortable images in sharp questions to lawyers on both sides. The issue: whether Congress was within its rights when it banned a procedure opponents call partial-birth abortion, for which there is little hard data and much disagreement.

“Wouldn’t the fetus … suffer a demise in seconds anyway?” Justice Stevens asked, focusing on the law’s ban on how, rather than whether an abortion may be performed.

Solicitor General Paul Clement replied: “Well, it may be seconds, it may be hours.”

“Do you not agree that it has no chance of surviving, in most cases?” Justice Stevens asked again.

In an intense morning of arguments, lawyers for the Bush administration and supporters of abortion rights gave starkly contrasting views on the practice: A law passed by Congress and signed by President Bush in 2003 labels it gruesome, inhumane, and never medically necessary. Supporters argue that such abortions sometimes are the safest for women.

An anti-abortion protester in the audience began shouting midway through the first of two hours of arguments, briefly disrupting the hearing before police dragged him away.

A day after voters defeated abortion restrictions in three states, hundreds of protesters gathered in the rain outside the court. Anti-abortion advocates curled up in the fetal position along the wet sidewalk, forcing pedestrians to step over them as abortion rights groups chanted and held signs nearby.

The Bush administration is defending the law as drawing a bright line between abortion and infanticide. The method involves partially extracting an intact fetus from the uterus, then cutting or crushing its skull.

Doctors most often refer to the procedure as a dilation and extraction or an intact dilation and evacuation abortion.

The procedure appears to take place most often in the middle third of pregnancy. There are a few thousand such abortions, according to rough estimates, out of more than 1.25 million abortions in America annually. Ninety percent of all abortions occur in the first 12 weeks of pregnancy and are not at issue. Six federal courts have said the law is an impermissible restriction on a woman’s constitutional right to an abortion.

Eve Gartner, arguing on behalf of Planned Parenthood Federation of America, said, “What Congress has done here is take away from women the option of what may be the safest procedure for her. This court has never recognized a state interest that was sufficient to trump the women’s interest in her health.”