ANNAPOLIS, FEB. 16 (SATURDAY) -- In a rare early morning session today, floor leaders in the Maryland House announced agreement to consider one more amendment before taking final action Monday on a Senate-passed bill guaranteeing continued access to abortion.

The agreement, announced shortly after 12:30 a.m., came after antiabortion leaders had begun delay tactics to stall passage of the controversial measure and amid pressure from Gov. William Donald Schaefer to approve the bill in the form the Senate approved earlier this week.

Friday afternoon, antiabortion lawmakers succeeded in delaying a vote on the bill when abortion-rights advocates failed to muster the two-thirds majority needed to prevent parliamentary maneuvers aimed at postponing the vote by the full House. A clear majority in the House favors the bill, which also requires that minors notify a parent before an abortion.

Schaefer on Friday issued a strongly worded statement urging the House to approve the bill swiftly and avoid what he termed the kind of "divisive" debate that led the Senate into an eight-day filibuster on an abortion measure last year.

"I stand ready to sign this legislation, if approved by the House in its present form," said Schaefer, who for weeks had avoided taking a stand on the bill despite his general support of abortion rights. "It is my hope that the House will take swift action."

Apparently heeding Schaefer's admonition, leaders of the two sides in the House announced that on Monday there will be a vote on one more amendment, which would preserve legal immunity under the so-called conscience clause for medical workers who choose not to refer a woman for an abortion.

Much of the bill mirrors the Supreme Court's 1973 Roe v. Wade decision, which guaranteed women the right to an abortion. The bill was promoted, in fact, as a replacement for the landmark ruling in case the high court one day overturns Roe. There would be no restrictions on adult women's abortions up to the time the fetus could survive outside the womb. Later, abortions would be allowed to protect the woman's health or in the case of a serious fetal deformity.

However, the measure would require that one parent of a girl under age 18 be notified before an abortion. A physician could decide against informing the parent if the physician believes the girl is mature enough to make her own decision or could be abused, or if an abortion is in the girl's best interest.

Passage of the abortion-rights bill was blocked Friday as antiabortion lawmakers used a parliamentary delaying tactic. Earlier Friday, the House had rejected by wide margins four amendments, including proposals to ban abortion for the purpose of birth control or sex selection.

The delay began when the House considered the only remaining amendment, the one on referrals. Under the measure, doctors and some other licensed health-care professionals would be required to refer women to abortion providers when continued pregnancy poses an unusual health risk. In cases involving purely elective abortions, the amendment would not force someone to tell a woman where she could get an abortion if it was contrary to the person's personal beliefs, according to the Attorney General's Office.

"I don't think anybody thinks a woman should die just because she's pregnant," said Del. Nancy K. Kopp (D-Montgomery), an abortion-rights supporter.

Up to now, Maryland law had given doctors and hospitals immunity from lawsuits or disciplinary action under a conscience clause if they declined to make an abortion referral.

Leaders of hospitals affiliated with the Roman Catholic Church, which opposes abortion, had lobbied heavily against changing the conscience clause. Del. Timothy F. Maloney (D-Prince George's), an antiabortion leader in the House, said hospitals could be exposed to lawsuits and employees could face disciplinary action.

"This has implications to every Catholic hospital and every person of conscience . . . who feels they cannot refer for an abortion," Maloney said.

An amendment to keep the conscience clause intact was defeated in the House Thursday night, 73 to 60. But on Friday, Del. Martha S. Klima (R-Baltimore), an abortion opponent, proposed a similar amendment and asked that the proposal be "laid over" for one day.

Such motions are frequently used, often by the minority on a given issue, to delay action on House bills, and they were common during the wrenching 1970s debates in the General Assembly over reinstating the death penalty. Usually, the one-day postponement is granted as a courtesy.

But in a move that veteran legislators said they had not seen in more than a decade, Majority Leader D. Bruce Poole (D-Washington) then sought to suspend the rules to prevent the delay. After an impassioned debate, the House refused, by a vote of 82 to 50, to go along vote. Poole needed 94 votes to suspend the rules.

"This is a matter that's not new to any of us," Poole argued. "We're not trying to ramrod this down anybody's throat. Full debate is fine; undue delay is not."

"They're just seeking to frustrate the will of the majority," said Del. Samuel I. Rosenberg (D-Baltimore), an abortion-rights leader.

Speaker R. Clayton Mitchell Jr. (D-Kent) said afterward that he ordered the unusual midnight session because only one amendment was pending at the time. "I thought it was important to bring them back and conclude it right away," he said.

Some lawmakers complained bitterly about the tactics used to press for quick action on the abortion bill, noting that the 90-day session is less than half over.

"In all the years I've been in the legislature, I've never heard threats like {a midnight session} made," said Del. Paul E. Weisengoff (D-Baltimore), who was first elected to the House in 1966. "I see hard feelings developing."