A ranking Soviet official suggests Moscow has moved to caution Israel, via the United States, against ''aggression'' that would trigger newly installed Soviet antiaircraft missiles in Syria.
''The American government has been informed what will happen with the missiles in the event of (Israeli) aggression,'' the official told The Christian Science Monitor.
''We assume this has been passed on to Israel. And in the event of aggression , everything will go as planned.''
He said the new missiles - SAM-5 antiaircraft batteries reportedly manned by Soviet personnel - were ''a purely defensive system.'' But he declined to specify under what conditions the weapons would be fired - for instance, whether an Israeli-Syrian clash in neighboring Lebanon would trigger them.
He said this was a ''military question,'' while the installation of the missiles was ''of primarily political importance,'' as a show of Soviet commitment to Syria in the wake of last year's Lebanon war.
''We are not looking for renewed conflict in the Mideast,'' the official said. He argued the US ''would have acted in the same way'' in demonstration of support for an ally following the Israeli invasion of Lebanon.
Syria lost much Soviet-made weaponry to Israel in the 1982 war. A less sophisticated SAM (surface-to-air) antiaircraft system that had been stationed in eastern Lebanon and operated by the Syrians was a prime victim.
Diplomats here say that in the intervening months, Moscow has also supplied Damascus with substantial numbers of new tanks and with what one envoy termed ''significantly more sophisticated electronic equipment.''
While the Soviet news media followed the dispatch of the SAM-5s by sounding alarm bells of allegedly imminent Israeli attack on Syria, the tone of more recent commentaries has been lower key.
Middle East correspondent John Yemma reports:
Israel and Syria are adversaries in a cold war that is heating up along with the Middle East weather.
The most troubling problem is the recent Syrian installation of 12 new batteries of long-range Soviet SAM-5 antiaircraft missiles inside Syrian territory. Manned by Soviet soldiers, the SAMs have an effective range of at least 150 miles, thus blanketing the skies of Syria, Lebanon, northern Israel, and parts of the eastern Mediterranean.
Israeli officials earlier had said the missiles posed no real threat to the Israeli Air Force. Reports this week in the Israeli press, however, have suggested that the missiles actually are more dangerous than had been thought.
What is at stake is the issue of Israel's maintenance of air superiority in the region, especially over Lebanon, where Israeli soldiers are deployed. The Israeli military will not tolerate Syrian MIGs over Lebanon and regularly has intercepted and downed them. A situation of parity is unacceptable to the Israeli military.
In view of this policy, the underlying fear is that Israel may be tempted toward a preemptive strike against the Soviet missiles in Syria. And if this were to occur, the Soviet soldiers manning the installations might be harmed. This, in turn, could precipitate heavier Soviet intervention in Syria and possibly a crisis between the two superpowers. Already, American Secretary of Defense Caspar Weinberger has estimated that there are 4,500 Soviet military personnel in Syria, including those manning the SAMs.
Also disquieting have been statements by Israeli officials predicting armed clashes between Israeli and Syrian troops in Lebanon as weather improves. If the clashes are major, the Israelis will want air cover, and, to achieve it, Israeli warplanes might go after Syria's Soviet antiaircraft missiles.
Since Syria follows an idiosyncratic policy line in the Arab world, an Israeli attack on the Syrian missiles - or on Syrian positions in Lebanon - probably would not cause much more than a halfhearted outcry from other Arab states. Syria's adjacent Arab neighbors, Jordan and Iraq, are bitter enemies.
A commentary on Jordan radio recently singled out the Syrian deployment of the SAM-5s for especially harsh criticism: ''Damascus' belief that the setting up of the 12 SAM-5 missile batteries gives it a free hand in the region . . . is ridiculous.''
Labeling Syria an enemy of ''the Arabism of Iraq, the Gulf, and the peninsula'' for supporting Iran, the commentary added: ''the mere presence of 12 sophisticated missile batteries cannot suddenly change the Arab political and military position from bad to good.''
Even if Syria is odd-man-out in the Arab world, however, Israel may not find it easy politically or militarily to move against Syrian forces in Lebanon or, as a prelude, the Syrian missiles. The Syrians consider the Bekaa Valley, which they now occupy, the backdoor to Damascus and would not be quick to abandon it to allow Israeli forces within 20 miles of the Syrian capital.
Israel would also have to worry about overextending its military and lengthening supply lines, thus making Israeli soldiers more vulnerable to guerrilla attack than at present. And scarcely a day goes by that Israeli soldiers in Lebanon are not attacked.
But possibly the biggest obstacle in Israel's way would be American disapproval. Israel already is under heavy pressure from the Reagan administration to pull its forces out of Lebanon. To gobble up more Lebanese territory and/or to precipitate a superpower crisis might cause a deep and lasting rift between Washington and Tel Aviv.