The president of the Maryland Senate has said he will introduce legislation in January that would ease restrictions on the public funding of abortions for poor women, an action that is expected to reignite one of the General Assembly's most volatile issues.

Honoring a pledge he made last year when the Senate rejected outright an attempt by the House of Delegates to remove abortion limits in force since 1980, Senate President Melvin A. Steinberg said in a telephone interview this week that he will ask the legislature to grapple with the issue in a separate bill rather than within the state's budget, the traditional battleground.

The language Steinberg intends to propose is similar to that pushed unsuccessfully two years ago by Gov. Harry Hughes, who sought to remove restrictions that prochoice advocates said had cut in half the number of Medicaid abortions and unfairly penalized poor women. Although less restrictive than current rules in effect since 1980, Steinberg's proposal also is less liberal than the guidelines approved by the House last year but rejected by the Senate.

As in the past, the coming debate over abortion is expected to center on the conditions under which state Medicaid funds will pay for abortions to protect the mental health of the mother. Maryland consistently has allowed publicly funded abortions for poor women in cases of rape, incest and when the life of the mother is in jeopardy. But, since 1980, the state has paid for abortions to protect the mental health of the mother only in cases when a physician certifies in writing that carrying the baby to term would have a serious effect on her mental health.

Steinberg's bill would remove the requirement for written certification, and refer only to the health of the mother, rather than her mental health. If adopted, Steinberg's legislation presumably would make more poor women eligible for state-funded abortions. In fiscal 1984, the last year for which figures are available, Maryland paid for 3,450 abortions at a cost of about $1.7 million, compared with 6,500 in 1979, the year before the current restrictions went into effect.

John Folkemer, chief of policy analysis for the state health department, predicted that Steinberg's bill, if approved, would result in "some increase" in the number of publicly funded abortions in a state that already has "more liberal language than the average state." But Folkemer said the number is unlikely to rise again to pre-1980 levels because of a decrease in the number of medical facilities participating in the Medicaid program.

Although the anticipated fight over abortion funding is expected to resemble the always emotional arguments of past years, there will be one crucial difference. In the past, the legislature has set abortion-funding policy by inserting language into the state's operating budget, thus guaranteeing a vote on the issue every year and often disrupting the budget process. This time, Steinberg is seeking to set the policy by separate statute, an action that raises the stakes for both sides since it would be more difficult to change once the policy is a part of state law.

"Whatever gets enacted in statute will certainly carry much more weight than the [budget] amendment process," said Steven Rivelis, a lobbyist for an umbrella organization of prochoice groups known as Marylanders for the Right to Choose.

Steinberg, who wants the abortion question debated on its merits without being entwined with budget issues, predicted a Senate filibuster is an "absolute certainty."

At first blush, Steinberg's proposal pleased neither side in the abortion debate. State Del. Patricia Sher (D-Montgomery), who led the House push for more liberal rules last year, said, "We will continue to fight for more liberal language." And Del. Timothy F. Maloney (D-Prince George's), who has often carried the antiabortion standard in the House, rejected Steinberg's proposal as no better than "removing the language altogether."