United Nations, N.Y. — The Security Council today is expected to renew the mandate of UNIFIL (the United Nations Interim Force in Lebanon) for three months. Since 1978 the UN force has been stationed in southern Lebanon, between the Litani River and the Israeli border. Its role has been to serve as a buffer between Palestine Liberation Organization forces and Israel.
Lebanon recently suggested that the UN force's role be enhanced and that it be authorized to help the Lebanese government consolidate its hold over the whole Lebanese territory. There was strong resistance to this at the UN.
Well-placed diplomats said that:
* Israel, rather than Lebanon, was the author of this plan. The idea being to leave southern Lebanon essentially under the control of the Lebanese Army into which Maj. Saad Haddad's pro-Israeli force would be integrated.
UNIFIL would not be in a position of ''nosing around'' in the area of most direct concern to Israel. Rather, it would be sent north, to Beirut and possibly to Tripoli, to shield the Lebanese government against the remnants of the PLO and possibly armed Lebanese opponents of the regime.
* Such a mandate for UNIFIL might not be in accordance with the ''philosophy'' under which UN peacekeeping forces are supposed to operate. They are intended as buffer forces between hostile countries and armies, not as a police force between rival factions inside a country, which is what they would become if they were stationed around Palestinian camps or in areas where various Lebanese Muslim groups would defy the government.
Both the United States and the Soviet Union were cool to the project.
As far as the US is concerned, the plan is premature. ''There are too many loose ends,'' a US diplomat says. But Western sources say they would not be surprised if the US supported the Lebanese project at a later stage, once Israeli-Lebanese negotiations have reached a more advanced stage.
The USSR reportedly objects for two reasons:
1. Officially, because it would place Syrian and Israeli forces on equal footing. Syria, in Moscow's view, was invited into Lebanon, whereas Israel came in as an invader.
2. Unofficially, because the project might be part of an American-supported Israeli grand scheme for striking a Camp David-type deal with Lebanon aimed at freezing Syria out and imposing a Pax Israelia on the Middle East.
Lebanon has at least for now put its plan back into the drawer, but the Lebanese may bring the plan back in three months when the UNIFIL mandate comes up again.