At first glance, the whole proposition seems bizarre.
The United States is considering a plan that could place it in the position of helping to provide a military escort that would protect members of an organization - the Palestine Liberation Organization (PLO) - which has long been hostile to the US and its ally, Israel.
American military involvement in Lebanon is by no means certain. A Pentagon spokesman said late Thursday, July 8, that there is still ''great doubt'' troops would be sent. Still, President Reagan has approved the plan ''in principle,'' and it is still under active consideration.
Given the obvious risks, why would President Reagan want to engage in such an operation? The reasons that the administration has stated are these:
The Lebanese government has requested American help in arranging for the evacuation from Beirut of the PLO. American agreement in principle to this idea would give more flexibility to Philip C. Habib, the chief US negotiator in Lebanon. The departure of the PLO and other foreign forces would allow for the revival of a sovereign Lebanese government and would eliminate the PLO threat to northern Israel.
American officials say that all of the above calculations are indeed at the top of their list as they push ahead with plans to get the PLO, the Syrians, and the Israelis out of Lebanon. But there are other reasons that the Reagan administration - together with France - has expressed a willingness to risk soldiers' lives in an attempt to extract the PLO from the Lebanon morass.
The following set of assumptions and calculations are usually unstated because any false step or declaration might upset the delicate negotiations involved. They lie behind President Reagan's high-risk decision to commit US marines, if necessary, to a peacekeeping role:
1. The US sees no good coming out of a massacre of PLO officials and soldiers - not to speak of innocent Lebanese and Palestinian civilians - through an Israeli attack on west Beirut. It wants to prevent that at all costs. The US wants the Israelis to pull back from the immediate Beirut area as one of the first steps in a package deal. Israel is not likely to trust any military ''screen'' other than American.
2. The US agrees with the Saudis and other Arabs whom the administration considers to be moderates that a total humiliation or crushing of the PLO would lead to a further ''radicalization'' of the Palestinian nationalist movement. A desperate PLO might directly threaten moderate Arab regimes friendly to the US. And its plight could help discredit those regimes in the eyes of their own people. In desperation, PLO remnants might turn increasingly for support to the militant regime in Iran.
3. Leaving aside the Israelis, more than a few of the parties to the Lebanon conflict profoundly mistrust each other and apparently require some kind of superpower guarantee that they will be protected from each other as they disengage. If the Palestinians agree to withdraw from Beirut, they will be in a highly vulnerable position, exposed not only to Israeli firepower but also to Lebanese militia allied with the Israelis. Although it has still not been agreed that the PLO would depart by sea, that kind of exit, under US and French protection, would allow the PLO to avoid the possibly more humiliating and risky procedure of moving by land to Syria.
4. The alternatives to the use of US and French forces would be a United Nations-sponsored international peacekeeping force or deployment of the Lebanese Army. The Reagan administration hoped at first that the Lebanese Army could do the Beirut peacekeeping job, but decided in the end that this army was still not strong enough to take on that task, sources say. US officials think that an international peacekeeping force under UN auspices would take too long to be formed. And, in the US view, even if it could be formed, it might have the disadvantage of being subject to Soviet involvement or veto. Meanwhile, the Israelis have made clear their objections to an UN sponsored disengagement from Beirut.
Beyond the immediate question of Beirut, the Reagan White House does not appear to have thought through the long-range alternatives, particularly when it comes to coping with the Palestinian question. The Saudis and the French urge a move in the direction of Palestinian self-determination on the West Bank and in Gaza. The Israelis are opposed. White House officials do not give any clear indication that they know how to proceed beyond perhaps reasserting the importance of dealing with the Palestinian issue.
''The groundwork on this is already done, but trying to get it up to the higher levels is a problem,'' said a State Department specialist. Specialists say that without some movement on the Palestinian issue, through renewed negotiations on the question, the US will be seen by Arabs as simply acquiescing in, or supporting, another Israeli aggression against Arabs. But some officials also privately admit that the Reagan administration has thus far been locked into a pattern of reacting to events, rather than taking the lead with positive gestures such as would be required on the Palestinian issue.