Lebanon's President Amin Gemayel is looking to the United States to use its naval guns to turn the tide in Lebanon. But many analysts here say they believe that the hard-pressed Lebanese leader is pursuing an illusion. They argue that the primary purpose of the US naval gunfire in recent days has been first to deter threats to the US Marine withdrawal and second to signal continuing American support for the Lebanese government.
That deterrent use of force and signals is a far cry from the decisive use of power which Gemayel seems to be expecting, or at least hoping for. Gemayel appears to be misreading the American political climate.
Alfred Mady, a key Maronite Christian leader who is close to President Gemayel, argues, however, that the United States has the power to intimidate Syria and halt the military drive being carried out by the Syrians' allies in Lebanon. Mr. Mady recommends that the US Navy destroy Syrian artillery pieces and cut two main supply routes leading from Syria through the Shouf mountains to the outskirts of Beirut.
On Thursday, an American destroyer fired on Syrian positions. This followed Wednesday's barrage, which included more than 200 rounds from the 16-inch guns of the battleship New Jersey, against Druze and Syrian gun batteries. A Marine spokesman said that shelling was directed at guns ''in Syrian-controlled Lebanon which have been firing on the city of Beirut.''
''If the New Jersey continues firing, then the (Lebanese) army can handle the fighting on the ground,'' Mady said in an interview. ''If you can cut their supply routes . . . and take out their artillery, then the army can move.''
''But if this is a cut-and-run policy - if you hit the Syrians for only a week and then the marines go away, the whole thing will collapse, and you'll be looking at a different Lebanon,'' Mady said.
He indicated that behind-the-scenes negotiations were going on among the parties to the conflict and that a ''kind of decentralized system'' might be at the heart of any reconcilation agreement. The Shiite Muslims, who constitute the largest sect in Lebanon, are obviously ''the new force'' in Lebanon's political equation, Mady said.
''The Sunnites are out of the game,'' he said, referring to the Sunni Muslims.
He said the May 17, 1983, Lebanese-Israeli agreement for the withdrawal of Israeli forces had to be abrogated as part of a Lebanon settlement. The Syrians have been demanding such an abrogation as they feel the agreement makes too many concessions to Israel.
In Santa Barbara, Calif., meanwhile, administration spokesmen have been stressing that the planned withdrawal of US marines to ships off the Lebanese coast does not diminish American resolve to defend the Lebanese government.
''I don't think there should be any misimpression by the government of Syria that there has been any lessening of the determination of the United States government to support the government of Lebanon,'' said White House spokesman Larry Speakes on Wednesday, the day the battleship New Jersey and the US destroyer Caron opened fire in what has been described as the heaviest American naval barrage since the Vietnam war.
On Thursday, Defense Secretary Caspar W. Weinberger told the House Foreign Affairs Committee that the US is ''not leaving Lebanon'' and that the decision to strike positions around Beirut with naval gunfire proved the point.
Mr. Weinberger rejected reports that the Lebanese army had disintegrated, but the secretary acknowledged that the prospects for an early reconciliation among the Lebanese political factions remained dim.
Judith Kipper, a Middle East expert at the American Enterprise Institute, said in an interview that what the United States must do is stop shelling and start talking. Ms. Kipper, who recently returned from a trip to the Middle East, argues that while American diplomats have had discussions with the most prominent Lebanese political leaders, they must go beyond that and engage in intensified talks with religious authorities and the ''real leaders'' behind the apparent leaders of Lebanon's many factions.
If this is done, Ms. Kipper says, some kind of reconciliation in Lebanon is still possible.
She adds that while Soviet-backed Syria would obviously exert a major influence in the situation, it need not dominate, because Lebanon's Shiite Muslims are ''too resilient'' and ''too nationalistic'' to accept Syrian control.
She argues that the shelling by US Navy ships off the Lebanese coast damages the chances for a political settlement, because the shells have not been hitting Syrian positions but those of the Lebanese Druze.
Adm. Stansfield Turner, a former director of the US Central Intelligence Agency and one-time commander of a Sixth Fleet carrier task group, said he was opposed both to the use of naval gunfire in Lebanon and to the plan to protract the withdrawal of the Marines.
In a telephone interview, Admiral Turner said that the use of the guns and the attempt to stretch out the withdrawal over a period of some months were both ''political moves designed to lessen the impression that we are withdrawing support from the government of Lebanon.''
Turner, who served in Vietnam, said he doubted that naval gunfire and air power would be effective unless they were used in close support of ground troops. He said that by protracting the Marine withdrawal, the US was encouraging terrorists to ''get moving now'' with any plans they might have to strike again against the marines.
''There is very little in the historical record,'' he said, ''to show naval gunfire or aerial bombing can turn the tide of battle in this kind of situation when we don't have ground forces engaged.''