King Hussein is willing to wait until after next fall's U.S. elections before pressing his case for buying sophisticated U.S. warplanes and a mobile Hawk missile system, an authoritative source said today.

The monarch's patience allows the Reagan administration to avoid letting the Jordanian arms requests become a hot issue in the congressional voting despite Israel's vehement opposition to such a sale, while at the same time keeping it on the agenda for later consideration.

"The Jordanians know how the U.S. political system works," a diplomat here said. "They're not dummies."During a trip to Washington last November, Hussein has expressed interest in buying F16 warplanes, perhaps along with F5Gs, and mobile, improved Hawk antiaircraft missile batteries. Because these would make his Air Force less vulnerable to Israel's currently overwhelming air superiority, Prime Minister Menachem Begin's government has vowed to oppose the sale in the U.S. Congress.

Against this backround, the U.S.-Jordanian joint military commission met last week in Amman, with Assistant Secretary of Defense Francis West leading the American side and Hussein the Jordanian side. Hussein subsequently expressed "frustration" at the administration's reticence, the source said, but withheld putting forward a formal request for the new equipment because of the political atmosphere in Washington.Secretary Caspar W. Weinberger suggested during his visit here two months ago that the United States would sell Jordan the highly advanced F16s and the improved missiles as part of the Reagan administration's effort to broaden its base of support in the Middle East and in part to thwart a planned Soviet-Jordanian arms deal.

Nevertheless, the administration is believed eager to avoid the kind of political battle that surrounded sale of less sophisticated Hawk missiles to Jordan in 1975. That controversy was settled by making the missiles immobile in concrete, a restriction Hussein has since described as "intolerable."

The Jordanian monarch already has announced his intention to buy SA8 antiaircraft missiles from the Soviet Union, a purchase the Reagan administration is seeking to head off. Diplomatic sources said that, technically at least, Jordan could buy the SA8s for low-altitude protection while still buying the improved Hawk system from the United States for higher-altitude coverage. But, they suggested, political realities would make it more difficult for Washington to agree to sell improved Hawks if Jordan goes ahead with the Soviet deal.

Hussein frequently has used the possibility of Soviet arms purchases as a tool to pry a more favorable attitude out of the United States. But informed sources in Amman say that more than ever he now is considering buying Soviet equipment if he cannot fulfill his needs in the United States. A team of Soviet specialists recently arrived here for talks on Jordan's interest in the SA8s, diplomatic sources reported.

Hussein and his military leadership are looking at Syria and the threat of Iranian-caused trouble in the Persian Gulf as the principal potential threats in the coming years, the authoritative source said. At the same time, the monarch is eager to have a more credible defense against Israel.

He is said to be particularly concerned about Syria. Jordanian intelligence reports say Damascus soon will have 1,000 Soviet-made T72 tanks, Moscow's most modern armored vehicle and rated by experts as among the best in the world. Syria deployed two armored divisions along the Jordanian border in the fall of 1980, when it was thought that Hussein might send reinforcements to Iraq in its war against Iran.

The Syrian government of President Hafez Assad also is an increasing political worry for Hussein, the authoritative source reported. On the one hand, the monarch deplores Assad's alliance with Iran against Iraq in a war that Hussein feels poses a threat to the entire Arab world, the authoritative source said. On the other, he worries about the apparent Syrian intention to frustrate any attempt to draw the Arab world together around a moderate alternative to Camp David that would include Egypt now that the Sinai has been recovered.

Saudi Arabia, in the name of the Gulf Cooperation Council it spearheads, sent a severe warning to Syria about 10 days ago, suggesting that Persian Gulf subsidies would be endangered if Assad continues his opposition to the rest of the Arab countries lined up with Iraq, knowledgeable sources said. But it remains to be to seen whether the Saudi warning will have teeth.

Hussein, at 47 a veteran of almost three decades on Jordan's throne, fears that an Iranian victory over Iraq could lead to a dangerous radical grouping of the Shiite government in Tehran, an Iraq run by like-thinking Shiite Arabs and the Soviet-backed Assad government dominated by Alawite Moslems, an offshoot of Shiite Islam.

This, he is authoritatively reported to feel, would pose a threat to the Sunni Moslem monarchies in the Persian Gulf oil countries--and Jordan. It also would provide a new channel for Soviet influence in the Middle East, the source said he fears.