The immediate future of new Arab diplomacy with Israel hinges on decisions to be made in Syria, according to administration officials monitoring the swiftly changing Middle East situation.

Syria's official media have reflected strong opposition to efforts by Jordan's King Hussein and Palestine Liberation Organization leader Yasser Arafat to unite for direct negotiations with Israel. The important question is how effective and sustained Syria's opposition will be. As Washington edged cautiously toward renewed engagement in Arab-Israeli negotiations, the State Department sent two friendly diplomatic signals to Syria about U.S. policy toward the Golan Heights and the gaining of freedom by an American journalist from Syrian-controlled eastern Lebanon.

U.S. policy makers are watching with unusual interest the trip to Damascus this weekend by Prince Bandar bin Sultan, the Saudi Arabian ambassador to the United States, who is expected to inform Syrian President Hafez Assad about the U.S.-Saudi discussions here last week and to probe Assad's position on the Jordan-PLO maneuvers. Bandar was a participant in the two working sessions last week between President Reagan and Saudi King Fahd and in other Saudi discussions with senior U.S. officials.

"There can be no war without Egypt and no peace without Syria," according to a statement about the Arabs attributed to former secretary of state Henry A. Kissinger. That maxim was cited last week by a senior Saudi official to explain Bandar's trip and Damascus' central role.

Syria bitterly opposed Egypt's peace treaty with Israel under the late President Anwar Sadat. Last week Damascus state radio denounced the Jordan-PLO "framework for joint action" as a path "similar to Sadat's [and] paved by concessions, humiliation and capitulation."

Arafat, who was kicked out of Syria after a break with Assad in mid-1983, is expected soon to submit his and Hussein's "framework" for negotiations with Israel to several PLO governing bodies in Algiers and Tunis. Arab sources said Arafat believes that he has majority support for the compromises he is proposing, despite public objections by several prominent PLO figures.

These sources said Arafat seeks near-unanimous backing for the Palestinian concessions aimed at getting the United States involved again in the peace process and at starting broad negotiations with Israel.

The opposition that Hussein and Arafat encounter will be affected by Syria, which retains a degree of influence with elements of the PLO and which in the past has employed military and paramilitary muscle to make things tough for foes.

To improve U.S. relations with Syria, the State Department volunteered in a public statement last week that the peace-for-territory bargain in the Middle East, encompassed in U.N. Security Council Resolution 242, applies to all Israeli fronts "including the Golan Heights."

The statement by State Department spokesman Bernard Kalb last Wednesday was intended as a "signal" to Syria, according to officials, although in substance it restates an established U.S. position. The Golan Heights, a strip of Syrian land slightly more than 10 miles wide, was occupied by Israel in the 1967 war and annexed over U.S. protests by Israel in December 1981.

Saudi Arabian policy makers, who had been urging a U.S. gesture toward Syria, expressed approval of Wednesday's Golan Heights statement and were expected to cite it in Damascus.

Israeli policy makers, especially those from the Likud Party whose government annexed the Golan Heights in 1981, strongly objected to the U.S. declaration. Foreign Minister Yitzak Shamir, head of the Likud faction of Israel's unity government, declared that the Golan is "an inseparable part of Eretz Israel" and is not negotiable. "Not even a statement by an American official will change this," Shamir said.

The gaining of freedom by American television journalist Jeremy Levin after 11 months of captivity in Syrian-dominated eastern Lebanon gave the State Department another opportunity to speak well of the Damascus regime. "The Syrians have played a positive role" in the effort to free Levin from his captors, believed to be pro-Iranian terrorists, State Department spokesman Edward Djerejian said Friday. He said the United States has "expressed our appreciation."

U.S. and Saudi officials said they considered the release of Levin unrelated to Fahd's trip or the revival of Mideast diplomatic activity. The same terrorists are believed to be holding a Saudi diplomat seized in Lebanon as well as four other Americans.

In another Mideast development, the State Department said reports indicated that Syria's Assad will not make an expected state visit to Iran in the near future.

U.S. relations with Syria, which is armed and backed politically by the Soviet Union, have been poor throughout the Reagan administration. Syria blocked implementation of the U.S.-sponsored Israeli-Lebanese accords of May 17, 1983, and was accused of masterminding military and terrorist opposition that brought about withdrawal of U.S. combat troops a year ago.

At the height of U.S. military involvement late in 1983, Syrian antiaircraft batteries in Lebanon fired on U.S. reconnaissance aircraft and American warplanes and ships attacked Syrian positions in return. The two nations at that point seemed close to expanding warfare.

Soviet support for Syria and the Soviet position on the Jordan-PLO "framework for joint action" are among the expected topics for U.S. and Soviet diplomats meeting Tuesday and Wednesday in Vienna to discuss Middle East issues. The State Department, mindful of fears that Washington and Moscow might make deals at the expense of regional powers, insists that the talks will be only "an exchange of views."

According to an Arab diplomat familiar with the thinking in Damascus, Assad argues that peace gestures toward Israel are doomed to failure now because Israel will not give up the occupied West Bank or the Golan Heights. The United States, he argues, is unwilling or unable to pressure Israel sufficiently to change this position.

Rather than negotiate now, Assad reportedly argues, the Arabs should build their military might to equal Israel's and try to diminish political support for Israel in the United States.

But Hussein and other "moderate Arabs" increasingly have accepted the U.S. view that the only way to peace is through direct negotiations with Israel, with active participation by the United States. Secretary of State George P. Shultz called repeatedly for such face-to-face Arab-Israeli negotiations last week. He said in a Voice of America interview Wednesday that when and if these parties sit down together, "I'm sure that they will want us to be present, they usually do, and we'll be glad to be present and try to be helpful."

The "framework" agreed upon by Hussein and Arafat lacks the clarity that Hussein had hoped for and which would elicit a clear-cut U.S. endorsement, according to State Department officials. But Shultz and others have described the potential "framework" as a step in the right direction. Statements from the White House and, in somewhat more muted fashion, the State Department, portrayed the developments as encouraging.

State Department officials said they anticipate a complex round of maneuvers in the Arab camp, with some central decisions likely to become clear by the time Egyptian President Hosni Mubarak arrives three weeks from now to see Reagan. Mubarak is among the most important and most vocal sponsors of the new negotiating efforts.

In private conversation, Shultz is reported to have cautioned the Saudis that the divisions on Palestinian issues within the two poles of the Israeli unity government -- Prime Minister Shimon Peres' Labor Party and Foreign Minister Shamir's Likud Party -- are such that any serious peace drive by the Arabs is likely to bring about a political shakeup in Israel.

Some Arabs appear ready to bring Israel's divided sentiments about negotiations to a test. Many Israelis, as well as a succession of U.S. administrations, have asked for such negotiations by the Arabs in vain for a long time.

Asked about Arafat's motivations in working with Hussein toward a common negotiating position, an Arab diplomat who has held lengthy discussions with the PLO leader replied, "There have been signals that Israel will be willing to negotiate and that the United States will get involved."

The diplomat said that Arafat, though weakened by divisions in the PLO, feels buoyed by the support for negotiations he is receiving from Palestinians on the West Bank, increasingly his most vital constituency.