The president of the Maryland Senate, who pledged last year he would introduce legislation to liberalize the state's rules on public funding of abortions, said yesterday he has changed his mind.

Sen. Melvin A. Steinberg, a Baltimore County Democrat, said discussions with his party leadership have convinced him that it would be unwise to seek the change through legislation rather than through the traditional route of placing language in the state budget, because any resulting law could be petitioned to a statewide referendum, sparking a divisive ballot fight in an election year.

Steinberg, who has been a prochoice advocate throughout his political career, promised last year to seek the change after the Senate refused to adopt House budget language that would have significantly eased the criteria under which the state would pay for abortions for poor women.

The Senate president also said that further reflection had convinced him that even if an abortion bill should pass, antiabortion legislators would still try to tighten rules through the budget. "It would create an exercise in futility," he said.

House Speaker Benjamin L. Cardin said he was "disappointed" by Steinberg's change of heart. "It's really going back on a commitment," said Cardin.

Steinberg's decision means that the almost annual battle over abortion funding will be fought once again within the budget, which in the 1985 session will be considered first by the House.