American hopes for the withdrawal of foreign forces and a political reconciliation in Lebanon are fading fast. Indeed, diplomats here now question whether the man who was supposed to pursue reconciliation - Amin Gemayel - can survive as President in Lebanon's current turmoil.
Much is likely to depend on talks between the Americans and the Syrians, who are seen to be holding the strongest cards in the conflict. President Reagan was reported to have instructed his special envoy, Donald Rumsfeld, to go to Damascus as soon as possible to try to achieve a political settlement and end the fighting. Reagan placed Vice-President George Bush in charge of coordinating ''crisis management efforts'' in Washington.
But the situation on the ground in Beirut has deteriorated so rapidly for the US-trained and supported Lebanese government forces that the American negotiating position is likely to be weaker than it was just a few days or weeks ago.
State Department officials said that US Embassy staff members in Beirut were being reduced to the ''skeleton'' level. As many as a half of the civilian staff members were to be sent home. US Navy helicopters lifted more than 40 staff members and their families to warships lying off Beirut on Tuesday after Muslim militiamen seized most of West Beirut.
As many as 1,000 Americans still remain in Beirut, however, which may be one reason why, as of this writing, there has been no move to withdraw the US marine contingent from Beirut. But the main reason given by the Reagan administration for the presence of the marines - and other members of the international peacekeeping force in Beirut - was to provide stability for a negotiating and reconciliation process. That process has now been cast into doubt by the fighting and by a hardening of Syrian demands as well as those of the Syrians' Shiite and Druze allies.
State Department officials indicate that there may be some ''give'' in the American position regarding the May 17 Lebanese-Israeli agreement which was negotiated with the help of US Secretary of State George Shultz. The Syrians have been demanding its abrogation, as it allows Israel a residual presence in southern Lebanon.
But some diplomats are now asking whether the revision, or even the abrogation, of that agreement would be enough to appease the Syrians. If their allies continue to hold the battlefield initiative, the Syrians may decide there is no need to compromise. The question for President Reagan will then be one of how far he is willing to go to support Amin Gemayel militarily.
Military experts doubt, however, that US naval gunfire or bombing by carrier-based aircraft would be sufficient to turn back the Muslim militia forces which now control West Beirut. The dispatch of American ground troops to restore the balance appears to be unlikely.
The air strikes and naval gunfire which President Reagan ordered on Monday against positions outside Beirut were limited in nature and described as aimed at protecting the marines at the Beirut airport.
On Tuesday, the US battleship New Jersey fired its five-inch guns in support of French paratroopers against Druze mortar and artillery positions.
It was the first time the New Jersey had used its guns in more than three weeks.
Polls show a growing public opposition to the US involvement in Lebanon. In a Washington Post/ABC television poll taken in January, 60 percent of those polled said they disapproved of President Reagan's handling of the situation in Lebanon compared with 30 percent who said they approved. A New York Times/CBS poll in late January found that 49 percent believed the US should withdraw from Lebanon as compared with 38 percent who said the marines should stay. The poll indicated that Lebanon is potentially the most dangerous foreign policy question facing President Reagan in this election year.
But one Reagan political strategist insists that the President will do what he thinks is in the long-term interest of the United States. If people raise the ''politics'' of the situation with Reagan, he reacts negatively, this strategist said.
Staff correspondent Julia Malone reports:
The Lebanese government crisis has put the brakes on congressional efforts to pass a resolution calling for the marines to withdraw from Beirut. House Democrats have decided to delay the resolution until at least late this month amid uncertainty about the latest developments.
But House Speaker Thomas P. O'Neill Jr. stepped up his appeal to remove the ground troops from Lebanon to nearby ships. ''I think it's time for the President to stop flexing his muscles,'' the Massachusetts Democrat said Tuesday.
''The time is long past for the administration to face facts and recognize that there is no role for the marines in Lebanon,'' said the speaker, who criticized the President for being on a trip to Las Vegas during the crisis.
O'Neill said the deteriorating situation in Lebanon requires - by President Reagan's own standard - the withdrawal of the marines from Beirut.
O'Neill recalled that Reagan said in early December the troops should be withdrawn if US goals were achieved or if there was a general collapse of order.
''I think it's reached that point,'' O'Neill told reporters. ''The Lebanese Army would seem to be falling apart.''
But most members of Congress, especially Republicans, preferred to wait and watch developments in Lebanon. As one House aide put it, ''I think they're going to shut up and watch for a while - and probably kick themselves for voting for the 18 months agreement'' which authorized Reagan to keep troops in Lebanon.