Following Prime Minister Shimon Peres' unprecedented public meetings with Moroccan King Hassan II, senior Israeli officials today conceded that there is "no possibility" at present of agreement on the Palestinian question on Hassan's terms. But they vowed to exploit the new opening in an effort to narrow the gap with moderate leaders throughout the Arab world.

"The Arab position is far away from our position, but in order to close the gap we need public dialogue and, later, public negotiations," said Peres' media adviser, Uri Savir, who traveled with the prime minister to Morocco for the three-day summit talks.

Describing the meetings between the two leaders as a "very significant historical event," Savir said the fact that a joint communique was issued by the governments of the two countries, which technically are in a state of war, "exceeded our expectations," even though, by his own characterization, the document was "vague on both sides."

"No one had any illusions, not on the Moroccan side and certainly not on our side, that within 48 hours it would be possible to bridge the gaps and it would be possible to solve the Middle East conflict. The importance was in the very readiness of the two sides to publish a joint communique, and this, in my opinion, is certainly a very important sign in itself," Savir said.

In Washington, State Department spokesman Bernard Kalb said the United States had not expected any dramatic developments in the Morocco talks, but he added: "The U.S. would hope contact between Arab and Israeli leaders would become more routine so that it would not be such a singular event when such leaders get together."

Asked about Hassan's statement Wednesday that the administration had offered to host the meeting in Washington, Kalb declined to answer directly. "We were willing to do whatever we could to facilitate the meeting," he said.

Israeli officials stressed that Hassan's insistence that the basis of a comprehensive Middle East peace plan must be the proposals adopted by Arab leaders in Fez, Morocco, in 1982, remains unacceptable to Israel. The Fez peace plan, while implying recognition of Israel, calls for Israel's withdrawal from all territories occupied in the 1967 Six-Day War, including East Jerusalem, and negotiations with the Palestine Liberation Organization. Peres, in a 5 a.m. news conference upon his return today to Ben-Gurion Airport, also suggested that the Fez plan cannot be a basis for negotiations, and said he countered by offering to conduct direct negotiations with Arab states without prior conditions.

"One must not forget that I'm not representing myself, or even my party. I'm representing a government which has a defined policy, and, surely, I have operated within the framework of the accepted policy of the present state," the prime minister said.

Peres has frequently said that no government in Israel, much less a fragile coalition government like the current one, could survive if it dared to propose an Israeli withdrawal from the occupied West Bank and Gaza Strip and East Jerusalem.

Sources close to the Peres-Hassan talks said that the Moroccan king, who is acting chairman of the 22-nation Arab League, stressed that the Fez peace plan represents the widest available Arab consensus. The king was also said to have stressed the importance of the 1974 Arab League conference in Rabat, which officially recognized the PLO as the sole legitimate representative of the Palestinian people.

Israel has steadfastly maintained that it will not negotiate with the PLO as an organization because of its adherence to an armed struggle against the Jewish state, although Peres has said that at least two well-known pro-PLO Palestinians in the West Bank and Gaza Strip would be acceptable in joint Jordanian-Palestinian negotiations that Jordan's King Hussein proposed in February, 1985. The proposal was dropped following an open split with PLO Chairman Yasser Arafat a year later.

The communique issued simultaneously today in Rabat and Jerusalem said Hassan had presented details of the Fez plan, "suggesting that this plan has the double merit of, on the one hand, constituting the sole document which is objectively valid as to serve as a basis for a just and durable peace and, on the other hand, being the object of an Arab consensus."

The communique added, "In his turn, Mr. Shimon Peres clarified his observations on the Fez plan . . . . As the meeting was of a purely exploratory nature, aiming at no moment at engaging in negotiations, His Majesty Hassan II will inform the Arab leaders, and Prime Minister Peres his government, of the points of view developed during the talks."

When pressed on what specific proposals Peres submitted to Hassan, Savir replied that the prime minister "presented the possibility of direct negotiations in the framework of an international forum, with a Jordanian-Palestinian delegation." Peres and his top aides seemed nonplussed by Hassan's televised speech last night, in which the Moroccan monarch said he had ended the talks with Peres after they "foundered" because of the Israeli leader's refusal to consider withdrawing from the West Bank and East Jerusalem or negotiating with the PLO.

"I think both sides were addressing different audiences, different constituencies," said Savir