It cannot but sadden the world that American diplomatic efforts to achieve a withdrawal of Israeli and Syrian forces from Lebanon have not proven successful. The most that US Secretary of State George Shultz obtained from President Assad in Damascus was an agreement to form ''working groups'' to continue exploring how to establish an independent Lebanon. Israel, for its part, is voicing its determination to remain in Lebanon indefinitely unless the Syrians get out.
Lebanon, in other words, is in effect being partitioned. The Israelis may elect to reduce their forces and pull back somewhat. But they will establish a permanent zone in southern Lebanon, while Syria continues to occupy most of the Bekaa Valley. This is the tragic legacy of Israel's invasion of Lebanon a little more than a year ago - the de facto dismemberment of a nation which, for all its internal weaknesses, wants to remain whole. Now it will take no less than a reinvigoration of US diplomacy in the Middle East - and a wholehearted commitment to the peace process - to restore the ''strong, free, sovereign Lebanon'' which Mr. Shultz and Mr. Assad say they want.
Fundamentally, the deadlock stems in part from a certain casualness in US policy and lack of knowledge about the region. The Reagan administration got off to a poor start by focusing first on the Soviet threat in the Middle East, neglecting the Palestinian problem altogether. Later it shortsightedly gave Israel a green light to invade Lebanon.Subsequently the outlook brightened when President Reagan became personally involved in the region with his plan for West Bank autonomy. But, unfortunately, the US failed to bring the Arabs and Israelis to the negotiating table - something it might have managed with more diplomatic muscle.
Washington did work out an agreement between Lebanon and Israel for a withdrawal of forces. But, even as the accord was being hammered out, experienced hands in Washington were warning that Syria would pose a stumbling block, that the US had for too long neglected President Assad and the crucial role he plays in the area. So it proved. On the face of it the Syrians may look to be the spoilers in the present impasse. But, from Mr. Assad's point of view, the Lebanese-Israeli agreement gives Israel political, economic, and military gains it has no right to demand as an invading power.
Will the Lebanese now learn to live with de facto partition? It is difficult to see how this process might be reversed short of a fresh diplomatic strategy. At the least, however, the US should not discourage a redeployment of Israeli forces in Lebanon if this means withdrawal from some Lebanese territory. A partial pullback seems better than no pullback at all. As for the areas that would be ''liberated'' in such a move, the Lebanese Army could be encouraged to take on the task of security, perhaps with US logistical support and the help of the multinational forces. Such direct involvement might begin to give the Lebanese Army the hardening and experience it so badly needs.
Beyond trying to keep the Lebanese situation as stable as possible, however, the United States needs critically to rethink its whole Mideast policy. Where is it going? What does it wish to achieve? Is it prepared to live with the new status quo, i.e., a partitioned Lebanon? Is it willing to ''cede'' the West Bank to Israel and, if not, what will it do about it? To state the obvious, a presidential election season is not an auspicious time for such a reassessment. But certainly someone in Washington should be thinking about the consequences of letting the Middle East drift. Past experience suggests the wisdom of avoiding such a course.