Louisiana Gov. Charles E. "Buddy" Roemer (D) yesterday vetoed what would have been the nation's most restrictive antiabortion law.

Last night, the state House voted, as expected, to override the veto, but opponents of the measure said they believed they have enough votes to sustain Roemer's veto in the Senate. The Senate voted to adjourn late last night rather than vote on an override.

Roemer, who opposes abortion, had told lawmakers he would veto any abortion bill that did not make exceptions for victims of rape or incest.

The Louisiana Human Life Act contains no such exceptions. It would allow abortions only to save the life of the woman and would sentence doctors who performed abortions to up to 10 years of "hard labor" and fine them as much as $100,000. It was designed to challenge the 1973 Supreme Court Roe v. Wade decision that legalized abortion.

At a news conference yesterday, the bill's author, state Rep. Woody Jenkins (D), called Roemer's veto "a slap in the face of the pro-life movement, which has supported him throughout his political career."

Jenkins said that of the 15,684 abortions performed in Louisiana in 1987, only one was "performed because of an alleged rape. . . . He's for killing 15,000 unborn children a year in Louisiana just to make sure that one child conceived in rape is also killed."

But Kate Michelman, executive director of the National Abortion Rights Action League, praised Roemer for vetoing what she said "would have been by far the most extreme law in the nation."

Opponents of the bill said they are confident the Senate will sustain Roemer's veto. The legislature is scheduled to adjourn by midnight Monday.

"In the Senate we believe that we still have the 15," said Robin Rothrock, an abortion-rights activist, referring to 15 senators who voted against the measure when it passed the Senate 24 to 15.

An override requires a two-thirds vote in each chamber -- 26 in the Senate and 70 in the House. The House initially passed the bill 74 to 27 and overrode the veto by a vote of 73 to 31. No Louisiana governor's veto has been overridden this century.