Morocco's King Hassan II surprised Arab diplomats and political observers tonight by announcing he will host an emergency Arab summit conference on Aug. 7 to discuss inter-Arab problems and the Palestinian issue.

Arab diplomats in Rabat, Morocco, and this Tunisian capital have been saying during the past two days that all plans for a summit meeting had been abandoned for lack of a consensus. Objections by Syria, Libya and Algeria had scuttled an earlier proposal for such a conference, which was to have opened Sunday in Casablanca.

Speaking in Skhirat, Morocco, at a press conference reserved for Arab journalists, Hassan said the rescheduled summit meeting would focus on "the improvement of the situation within the Arab nation and the Palestinian question. . . ." Tunisian television reported Hassan as saying that a majority of Arab states would attend.

The Arab League traditionally has avoided holding summit meetings in the absense of a consensus. Arab diplomats, who asked not to be named, said there was no indication that any of the countries recently opposed to a summit had changed its position.

"King Hassan is a clever man, and one supposes he has reason to think he will succeed, but nobody knows what new development might have led him to schedule a definite meeting," an Arab diplomat here said.

Both Hassan and the Palestine Liberation Organization leader Yasser Arafat called for a summit meeting last month when the Lebanese Shiite Amal militia, supported by Syria, fought to take over Palestinian refugee camps in Lebanon. Syria opposed the summit proposal, and walked out of a lower-level Arab League meeting that debated the fighting in the camps.

A Syrian objection to a new summit is linked to its opposition to Jordanian-Palestinian moves toward negotiations with Israel.