Prospects for deployment of a United Nations force in Beirut to replace the multinational forces are not bright in the immediate future. But such a possibility cannot be excluded in the long run.
Under the best of circumstances, it would take several weeks for the conditions under which the UN could send a peacekeeping force in Beirut to mature.
France is pressing hard for a Security Council meeting, which it hopes could lead to the decision to send UN forces or at least UN observers to fill the gap that departing members of the multinational force will leave.
High-level UN officials say that four conditions must be met for such a deployment to occur:
First, a request must come to the UN from the Lebanese government. Second, the warring factions in Lebanon must agree and welcome the UN forces. Third, there must be countries willing to offer troops for the new UN force. And fourth , the Security Council must agree and order the UN to send it to Lebanon.
''Right now, we have no Lebanese government, so to speak. The warring factions are shooting at, rather than talking to, each other. After what happened to the multinational force it is unlikely that many countries, if any, will offer their men to be stationed in Beirut. Nothing indicates that the Soviets are about to lift their veto at the Council and to make things easier for the Americans in Lebanon,'' says one high-level UN official.
In time, however, the Soviet Union may take a more conciliatory stance. ''Before it decides to slam or to open the door to a UN presence in Beirut, the Soviet Union wants time to assess the new situation,'' says a diplomatic source familiar with Soviet thinking.
''The next week or two will tell whether the redeployment of the Marines is to be followed by further 'positive steps,' whether the Americans will allow the Lebanese to come to terms with each other and to redistribute power among themselves in a more equitable way than had been envisaged by (Lebanese President Amin) Gemayel, or whether the US still intends to project its force in order to influence the baking of the new Lebanese cake in a way favorable to itself, and ignoring Syrian and Soviet interests.''
Until last week, the US was opposed to ''sending in the UN'' to replace the Marines. US officials are now mum on this issue but there are signs that both the US and Britain, along with France, might welcome the deployment of UN forces or observers in Beirut.
Under Secretary-General Brian Urquhart says that ''a UN force must have a broad political base.'' The Soviet position as of now is ''wait and see.'' In the end, the prospects for the UN playing a constructive role depend on:
* Whether the main Lebanese groups can patch up their differences;
* Whether the US acquiesces or not to Soviet and Syrian intersts, and accommodates them with its own and Israeli interests,'' as one Arab ambassador says.
Monitor contributor Robin Wright reports from Beirut that there would be pros and cons to a UN alternative. The most important ''pro'' is the UN's history for not getting involved with the use of force. A UN force would therefore not be seen as taking sides in the dispute - the charge against the US in Lebanon.
For example, the UN Interim Force in Lebanon (UNIFIL), has lost only 42 men in action in almost six years there. In comparison, more than 330 MNF troops have been killed in the past 16 months. But the lack of force to back up UN troops has also been a detriment, since it could fail to deter violence.
Another advantage to a UN force in Beirut would be its broad-based nature, with no superpower presence that would be politically sensitive. In UNIFIL, none of the participants - Italy, France, Ghana, Senegal, Sweden, Finland, Norway, the Netherlands, Fiji, Ireland - has long-term interests in Lebanon. On the other hand, the lack of superpower participation could reduce the political leverage of a UN mission in Beirut.