Beirut — The American air strike on Syrian positions in Lebanon Sunday is being seen here as potentially raising the stakes in President Reagan's campaign to restore the central Lebanese government's authority.
Washington has portrayed the strike, in which two United States jets were lost, as a simple reprisal for heavy Syrian antiaircraft fire against US reconnaisance flights over Lebanon Saturday.
But Arab political analysts here see the air strike, whatever its immediate catalyst, as signaling a new, generally tougher American approach to the Syrian presence here. Syria has an estimated 40,000 troops in east and north Lebanon, a force introduced after the 1975-76 Lebanese civil war.
''Until now, the Americans have been more careful (with Syria), playing by set rules. . . . Before, the Americans replied with words when the Syrians fired on planes. Now, the rules are new, it appears,'' one prominent Arab political analyst remarked hours after the US strike in the hills northeast of Beirut. Sunday's action was the first American air attack since the establishment of a US military presence in Lebanon after the 1982 Israeli invasion.
Three US pilots were forced to ditch in the strike. One was rescued by a Lebanese fisherman in the Mediterranean. The pilot's abandoned plane crashed in a residential area north of Beirut, injuring eight Lebanese. The other two US airmen, at time of writing, were missing and believed captured behind Syrian lines.
Various analysts also placed the attack - in which some two dozen US planes were involved - in the context of an American agreeement last week on closer military and political cooperation with Israel.
The Syrians, at least, are seen as bound to view the two events as closely and directly tied.
And since Lebanese President Amin Gemayel was, himself, in Washington days after the US-Israeli accord, he will likely be seen by his Syrian neighbors as at least tacitly in on the toughened US action against Syria.
Sunday's confrontation, itself, need not lead to a major new cycle of Lebanese violence.
For one thing, the Americans' loss of two jets allows Syria to claim a victory of sorts in the exchange.
''If Damascus wants to play things cool, that option is made easier by the fact the Americans lost these planes,'' remarked one Arab political commentator privately.
And while the heightened US-Syrian tension was expected to do no good for incipient efforts at national ''reconciliation'' within Lebanon, one oddly encouraging surface move on that score came only hours later.
The Lebanese Druze forces of Walid Jumblatt announced they would unilaterally free some 20,000 Christian civilians they have been holding as hostages in the central Lebanese hill town of Deir al Qamar during a war with the Christian Phalangist militia.
But most analysts' sights were set on the longer term.
Specifically, there was concern a fundamentally tougher US approach to the Syrians - coupled with more open and closer military cooperation with Israel - could further polarize the internal Lebanese political equation between the dominant conservative Christians and lefist, Syrian-allied Muslims and Druze.
A first round of reconciliation talks among the rival parties, held in Geneva last month, ended with apparently improved relations between President Gemayel and the Syrians. But he was also supposed to report back to his rivals - and Syria, an ''observer'' at the talks - about progress on winning an early withdrawal of Israeli forces from southern Lebanon.
On that score, progress will be slow even in the best of circumstances. Now, in addition, a toughened US stance on Syria's troop presence in Lebanon could fuel renewed tension between the Beirut government and Damascus.
Finally, some Arab analysts are concerned that both the Syrians and their Soviet military allies - aware of the US marines' vulnerable position and limited counterstrike options in Lebanon - may be tempted to respond to any sustained shift in US approach by mounting, or sanctioning, strikes against the US force.
This, in turn, may partly depend on the health of Syrian President Hafez Assad and Soviet leader Yuri Andropov, both of whom have been reported ill. Indeed, more than a few Arab political analysts here suspect this may have been one element in the US decision to mount Sunday's air attack.
Some analysts observed that the loss of American jets in combat was the first since the Vietnam war.
Daniel Southerland reports from Washington:
The clashes that have occurred between Syrian gunners and American fighter pilots in Lebanon are not just random events. They could mark a major escalation of the Lebanon war.
Reagan administration officials say that Syrian antiaircraft fire directed at two American carrier-based reconnaissance planes on Saturday was unprecedented in volume. In addition to using heavy conventional antiaircraft fire, the Syrians fired at least 10 surface-to-air missiles at the US planes, American officials said.
US reconnaissance planes have been flying over Lebanon for more than two months now. They have been fired on before, but in previous incidents, the firing was conducted in a much more random manner.
On Sunday, two dozen fighter planes from the US carriers Kennedy and Independence launched retaliatory strikes against Syrian antiaircraft positions. It was the first direct combat engagement between the US and Syrian forces in Lebanon.
The Syrians appear to have given their answer to the newly strengthened US-Israeli relationship of cooperation in Lebanon. The Syrian answer seems to come down to this: ''We cannot be frightened off. Don't try to push us around.''
Through their attacks on the American planes, the Syrians seem to be saying that President Reagan is bluffing, and that they are calling his bluff.
If this is indeed their attitude, it could lead to a whole series of clashes. Speaking Sunday on the ABC television program ''This Week with David Brinkley,'' US Undersecretary of State Lawrence S. Eagleburger said that the retaliatory strikes carried out by American planes on Sunday were strictly ''defensive'' measures.
''It is not part of some plan to push Syria out of Lebanon . . . ,'' said Mr. Eagleburger. ''It is not a consequence of some arrangement made with Israel.''
Eagleburger said that, according to information he had received, the US planes ''took out'' a Syrian command and control area and two antiaircraft sites in locations east of Beirut. ''I have been told that what we set out to do we achieved,'' said the undersecretary.
Asked if there was a danger of escalation in Lebanon, Eagleburger said: ''If we don't get shot at, we won't shoot at them.'' But he also acknowledged that ''these sorts of events are always dangerous.''
The State Department official repeated earlier administration assertions that the US marines are stationed in Lebanon to help provide a base for the strengthening of the government of Lebanon.
A Defense Department spokesman said that on Sunday the pilot of the single-seat Navy A-7 Corsair II was picked up after parachuting into the Mediterranean.
(Reuters reported witnesses as saying that one of the airmen in the downed two-man A-6E Intruder was killed when he parachuted from his aircraft, while the other was taken prisoner by the Syrian Army.)