The United States and the Soviet Union declared for the first time today joint objectives for a full Arab-Israeli peace settlement.

A statement issued simultaneously in new York and Moscow in the names of Secretary of State Cyrus R. Vance and Soviet Foreign Minister Andrei A. Gromyko called for "A comprehensive settlement of the Middle East problem" at a conference to start in Geneva "not later than December, 1977."

The declaration represents an extraordinary attempt by the superpowers, who are intense rivals in the Middle East, to push the Arabs and Israelis toward a settlement even though Moscow and Washington at this stage disagree themselves on the precise terms of an ultimate agreement.

On its face, the statement, which grew out of a Soviet initiative, leans more toward Arab terms for a conference and agreement than it does on Israeli conditions. The United States and the Soviet Union set out their own agreed principles in these joint guidelines:

Withdrawal of Israeli armed forces from territory captured in the six-day, 1967 war, which gave Israel control of areas held by Egypt. Jordan and Syria. The core issue - how much Israeli withdrawal - was not specified.

Resolution of "the Palestinian question" that would assure "the legitimate rights of the Palestinian people." This is a key code-phrase in Arab demands that the United States always has avoided before, at Israeli insistence.

Termination of "the state of war" and "establishment of normal peaceful relations" between Israel and its Arab neighbors. Israel has called for peace treaties and for normal relations with the Arab nations, not merely the end of belligerency after four wars starting in 1948.

Establishment of demilitarized zones with U.N. troops or observers to assure "the security of borders" between Israel and the Arabs, with possible international guarantees of the borders.

American and Soviet willingness to "participate in these guarantees," with the question left open on possible use of troops from the two countries to help enforce the guarantees.

All parties concerned and all questions" should be involved in the comprehensive settlement.

The U.S.-Soviet statement came after two weeks of extensive discussion by Vance and Gromyko, including two rounds of talks with President Carter.

Although the statement has no binding effect on the parties, it signifies a major escalation of combined efforts by the United States and the Soviet Union to work together to induce the Arab nations and Israel to accept a Geneva conference along these broad lines. American diplomacy in recent years has dominated Arab-Israeli negotiations at the expense of Soviet influence in the Middle East.

The Carter administration has been committed to an increased role for the Soviet Union in Arab-Israeli diplomacy on grounds that a Middle East settlement is unreachable without Soviet concurrence. Yesterday's statement was the product of negotiations that began with a Soviet draft, it was learned, although the two nations still disagreed on many specifics of a Middle East settlement.

Although the statement is loaded with ambiguities, it immediately aroused elation among many Arabs, and gloom among many Israelis, when it was circulated at Vance's headquarters hotel opposite the United Nations.

Arab interest centered on the most striking departure in past U.S. policy, the joint commitment to "the legitimate rights of the Palestinian people." To the Arabs, and to the Israelis, this connotes an ultimate Palestinian homeland or entity - if not a state. Israel is adamantly opposed to creation of a Palestinian state, the goal of th Palestine Liberation Organization, with which Israel refuses to negotiate on grounds that the PLO is committed to eliminating Israel.

State Department spokesman Hodding Carter III said. "The legitimate rights of the Palestinians are not to be purchased at the expense of Israel." This statement, he said, in no way represents a U.S. retreat" from the U.N. resolution 242, which indirectly acknowledges Israel's right to exist. The PLO has refused to accept that resolution.

Nor, Carter said, would PLO endorsement of the U.S.-Soviet statement constitute "an acceptance of our terms for talking to" the PLO, which have been based on acceptance of the U.N. resolution.

Asked what the United States means by the Palestinians' "legitimate rights," Carter said, "We are not trying to define what it means." That, he said, is up to the parties at Geneva.

This phraise, Carter said, must be read in conjunction with the statement in the declaration calling for establishment of normal peaceful relations between Israel and the Arabs.

The spokesman also said that in the statement the United States is not saying who the "Palestinians" are who should participate in a Geneva conference. The immediate barrier for reconvening the conference is Israel's refusal to accept the PLO as participant. Instead, Israel has said it will accept Palestinians in a Jordanian delegation who are not known members of the PLO.

On all these points of controversy, Carter, "the critical question is what the parties in the area are willing to do."

Vance, in Washington-New York rounds of shuttle diplomacy with Arab foreign ministers and Israel's Moshe Dayan, has been concentrating primarily on a formula to get the Geneva conference under way.

Israel has agreed to open talks with a single, unified Arab delegation that would include Palestinians, as the United States has urged. But Dayan has said that even if the PLO accepts U.N. resolution 242, "we do want want to talk to them or to negotiate with them," nor to discuss a "Palestinian entity" - which President Carter had advocated.

What Israel will discuss, with non-PLO Palestinians, Dayan has said, is how Israel will "live together" with them in the West Bank of the Jordan River and in the Israeli-occupied Gaza Strip, which Israel captured from Egypt in the 1967 war.

The present Israeli government of Prime Minister Menahem Begin has said it will never surrender to the Arabs the West Bank or the Gaza Strip. It has held out the prospect for relinquishing some further territory in the Sinai desert to Egypt and in some additional portion of the Golan Heights to Syria.

The U.S. Soviet statement today employed the same ambiguity on Israeli withdrawal from Arab territories that was used in U.N. Resolution 242 at the end of the 1967 war.

The Arab interpretation of this is that it means Israeli withdrawal from all territories. The Israeli position is that it does not mean that and the United States has agreed with a narrower interpretation, meaning that it calls for withdrawal from unspecified amounts of territory.

The United States position, however, unlike Israel's, is that Israel should retain only relatively small amounts of the captured territory.

The joint statement that emerged here today with the Soviet Union is described as a document that has been under study for some time, before the first meetings between Gromyko and the Carter administration in the last two weeks.

Vance and Soviet Ambassador Anatoliy F. Dobrynin are said to have discussed the idea before Gromyko arrived. Extensive bargaining was reported over the terms of the original draft proposed by the Soviet Union, which is now explained as the reason why the final language includes some new terminology that the United States never previously accepted.

The Soviet Union is said to have failed to get all of the language it wanted in behalf of the PLO position.

The idea for a U.S.-Soviet guarantee of an Arab-Israeli peace settlement has long been discussed. Although the statement makes no references to the possible use of American or Soviet troops in a U.N. peacekeeping force between Arab and Israeli lines, the administration's position is said to be that this will depend on whether the parties want superpower participation in the form of a physical, as well as a declaratory guarantee of an agreement.

Israel in the past has always sought to exclude Soviet participation in activity involving its vital interest, as the Soviet Union has supported the most militant of the Arab nations and organizations. The U.S.-Soviet statement, therefore, brings into the current situation a much greater degree of Soviet involvement than Israel ever favored.