A warning signal flashed on for Israel when the press ignored Ronald Reagan's sharply honed Aug. 21 statement attacking the Carter administration for not vetoing the U.N. resolution condemning Israel's Jerusalem takeover. f

Israel is now suspected here of planning other major moves against the Arabs under cover of the presidential campaign. The inability of Reagan and Democratic critics to make a headline political issue out of the non-veto argues for Israeli caution in its future moves.

These include intensification of Israel's cross-border attacks against Lebanon and a bold attempt at outright annexation of the Golan Heights. But sharpened skepticism in the United States about Israel's unilateral actions in Jerusalem, the West Bank and Lebanon may undercut Israel's traditional use of presidential campaigns to leverage its influence here so as to advance its cause against the Arabs.

Reagan's statement saying that the non-veto "appalled" him was not reported in newspapers here and in New York City, surprising his political advisers. Equally surprising was a private letter from one of Israel's champions in Congress, Rep. Ben Rosenthal of New York, to Secretary of State Edmund Muskie. Rosenthal praised Muskie for going to the Security Council in person with a hard-hitting statement attacking repeated U.N. efforts to pass "unbalanced and unrealistic resolutions" against Israel.

But Muskie's failure to veto the Jerusalem text was accepted by Rosenthal. "Within the context of the constraints operating upon our foreign policy," he wrote Muskie, "I understand the decision."

The new movies that U.S. officials believe are now being planned by Prime Minister Menachem Begin's government against Lebanon and on the Golan Heights should be judged by Israel against this rising skepticism in the United States. American public opinion in support of Israel can undermine a president's most cherished policies, as many a president has discovered to his sorrow. But without the backing of public opinion here, Israel could find its chosen course a rocky one.

The legal move aiming at Israeli absorption of the Golan Heights, which is by far the most daring now under consideration in Jerusalem, is being pushed by Geula Cohen, the same member of parliament who successfully won passage of the bill annexing Arab East Jerusalem.

The Golan Heights bill will come up for a vote when parliament reconvenes in October, and approval is by no means impossible. An editorial in the respected Jerusalem Post Aug. 1 asked: "Will Knesset (parliament) members again rush into folly, like lemmings to the sea, inevitably carrying the whole country with them?"

If the answer is yes, today's near-isolation of Israel in the world would become universal. If President Carter's decision not to veto the Jerusalem resolution could so easily escape public censure, annexation of the Golan Heights would inevitably face across-the-board condemnation in the United States.

Intensification of Israeli raids on Lebanon, in concert with Israeli-armed Christian militia, would continue longstanding Israeli policy that the United States has repeatedly but vainly sought to stop. A new political element has been added, however, by Israel's open admission that U.S.-supplied arms are used in these raids.

Administration officials will soon be summoned to testify on Capitol Hill whether the law prohibiting Israel from using American weapons except in self-defense is being broken. Some officials hope that will lead to a thorough congressional investigation to decide whether the cross-border attacks really are self-defensive or are aimed at territorial acquisition and the establishment of an independent pro-Israeli state in southern Lebanon.

For the Carter administration, the swing of public opinion away from automatic blessing of all Israel's actions is a two-edged sword. It makes it easier to resist Israel's demands, as in the Jerusalem resolution. But there is concern that as Begin feels more isolated, his propensity for dangerous unilateral actions increases. That could lead to a crisis extending far beyond the Middle East battleground.