What do we want in Lebanon?

The administration, beginning with President Reagan, is now expressing concern over the deployment of new and more sophisticated Soviet weaponry to Syria.

The concern is justified. Any escalation of the level and capacity of military equipment in the region can only complicate efforts to bring peace. The fact that they are there, however, may say something about our own approach to the problem of Lebanon.

Only a little more than a year ago, when the Israelis invaded Lebanon, many in the United States, including officials, were gloating over the defeat of Syria and the setback for the Soviet Union. The flawed assumption that the Israeli invasion would bring peace and the doubtful Israeli use of American arms were glossed over because so many believed the Israeli action to be a ''victory for our side.''

It will be hard for many to accept that our attitude at that time may have some bearing on the more sophisticated Soviet arms now flowing into Syria. Some will insist that the transfer of these weapons is just one further illustration of the long-range global ambitions of the Russians and the regional designs of the Syrians. The Soviet Union, however, up to now has not made available to countries in the Middle East its most sophisticated advanced weapons. To do so undoubtedly required a major policy review in the Kremlin.

It will also be hard for many to accept that Syria may be acquiring these arms because events of the last year and a half have increased that nation's doubts about the intentions of the Israelis and the US.

We tended to look at the Israeli invasion largely in terms of our confrontation with the Soviet Union. We may now be reaping the results.

Now, too, we are describing the presence of the US Marines in Lebanon, as the President did in his recent radio broadcast, in the context of stopping the Soviets. The original purpose, as part of a multinational force to permit the peaceful reconstitution of Lebanon, becomes forgotten.

We need to decide what we want in Lebanon: a long-range presence designed primarily to oppose the Soviets in the region or a peaceful Lebanon free of foreign troops and ultimately able to stand on its own.

The placing of the Lebanese problem in the East-West setting has three present and potential hazards.

1. It can only accelerate the spiral of arms, as the present shipments to the Syrians demonstrate. Had we made greater efforts to stop the Israelis and discourage the destruction of Syrian weapons, it is possible the Syrians would have had less justification for their latest request for arms. The new arms in Syria will now, undoubtedly, bring demands from the Israelis for more weaponry from the US, demands that will be hard for an administration openly concerned about the Syrians arms to refuse.

2. The East-West context can reduce the support of Arabs, including the Saudis, whom we need most in the diplomacy of Lebanon. The Saudis have some leverage on the Syrians as another Arab state. They will be less and less comfortable with their role and less and less effective if they appear to be acting solely as an American surrogate in opposition to the Soviets rather than as a mediator working for a politically viable Lebanon.

3. Our allies, particularly the French, are not likely to be comfortable with the way we describe the problem. They see the role of the multinational force in terms of their traditional interest in Lebanon.

The Israelis see advantages in picturing the Middle East problems in global terms, but, in reality, they see the problems as regional. Their ''communists'' are the PLO. Once that threat to Israel is contained, they look to their own security. That could, as some suggest, include even a tacit understanding with Syria to keep the status quo in Lebanon. A US policy that assumes an Israeli preoccupation with the Soviet threat could be mistaken.

As the recent months have demonstrated, the Lebanese problem is complicated. Perhaps, by close association with our allies, through the help of the Saudis, and by some understanding with the Syrians, a Lebanese accord of national reconciliation can be established. We were able to achieve this in 1958, although the situation was less complex then.

If, on the other hand, we see each development as a ''win for our side'' or a defeat for the other, we are likely to turn off the very support and confidence we need in the area. If we do that, we may achieve the objective of keeping the Soviets at bay, but our military forces may be in Lebanon for a long, long time.