The U.N. Security Council held its fourth straight public debate on the Falkland Islands crisis today and privately considered at least three different texts designed to promote a settlement. So far no formula has emerged that could satisfy both Britain and Argentina.

The three draft resolutions were circulated among the 15 council members by Panama, Ireland and Japan.

They all have in common a formal appeal to Secretary General Javier Perez de Cuellar to resume his mediation efforts, which collapsed last Thursday. The secretary general's aides say he would welcome a "mandate" from the council for such a task, but only if it is specific, and realistic, about what he is to do.

The approaches by Panama and Ireland both involve an end to the fighting. The Irish seek a 72-hour truce, during which the secretary general would negotiate terms for a continuing cease-fire. But Britain has indicated that it would veto any measure that prevents it from expanding--and holding onto--its beachhead on the islands.

The Irish proposal was to be submitted formally tonight. A vote could come as early as Tuesday evening, although none is anticipated as yet.

The Japanese text does not call for a halt in the fighting. It simply urges the secretary general to reopen talks on the basis of his previous effort, in hopes of achieving a cessation of hostilities and a settlement of the dispute.

Britain might buy this, diplomats said, but Argentina--which has been publicly noncommittal on the Japanese approach--is expected to ask its backers, including Panama and the Soviet Union, to block it. Even if adopted, observers here note, the Japanese resolution would have no practical effect. One Western diplomat called it "a placebo."

Observers say the Security Council appears to be groping for some solution that can resolve a central dilemma: it must do something or lose its credibility, although it recognizes that there is little it can do to stop the fighting before it runs its course.

The objective of Argentine Foreign Minister Nicanor Costa Mendez, who has been meeting with diplomats here since Saturday but thus far has neither participated in the public debate nor answered questions from the press, appears to be to win a majority vote for a resolution that Britain will have to veto.

Costa Mendez has no expectation that such a diplomatic result will end the fighting, but it would cast Britain in the role of the intransigent party.

Argentina then hopes to move the public debate from the council to the General Assembly, where Britain has no veto, and a majority can be found for a cease-fire resolution.