IT MAKES SENSE for the administration to send a squadron of unarmed F15s to reassure Saudi Arabia. One can suspect that the Saudis' fear of communist encirclement is overdone, or wonder what the United States might be called uponm to do for the Saudis, and if we would do it, in a showdown. Countries like Saudi Arabia, however, with their tradition of and need for dependence upon outside opwer, have a rather less complicated view of this sort of "gunboat diplomacy." When it is done in their behalf and, as now, at their behest, they find it bracing. Saudi Arabia is tranquil: The Saudis feel their domestic structure -- politically and in religious terms -- is stable enough to spare them Iran's spasms. Perhaps. Meanwhile, they see themselves as a tuna in an ocean filling up with sharks. Who is to say they are wrong?

The F15 case is different from the naval mission aborted a week ago. The administration had ordered a carrier task force based at Subic Bay to head toward the Persian Gulf, apparently to bolster the shah, but called it back in mid-passage. Notwithstanding the embarrassment of being seen to change signals, it was wise to halt the mission. The arrival of the carrier, with its th reat of direct military intervention, would have been taken in Iran as old-style American strong-arming in a context where past American intervention is one of the central grivances against the shah.

It is unthinkable that planes would have been sent into action in what is, after all, an internal dispute. But if planes had not been sent into action, the United States would have looked the very opposite of powerful. Surely even those other Persian Gulf countries, for whose reassurance Washington also sent the task force, would have understood that. The carrier should never have left port.

Americans look at Iran and anticipate turbulence elsewhere in the region of the Persian Gulf and Indian Ocean and ask how American power can usefully be brought to bear in the service of U.S. INTERESTS AND FRIENDS. Some fear, or derisively charge, that the United States has tied itself in knots; others (a smaller number) that the United States is too ready to throw its weight around. We think both viewpoints do the country a disservice. There are limits to the uses of power in and about the Persian Gulf, but there are possibilities, too -- real and sensible ones. Injecting American military power directly into a raging civil conflict, or threatening to, is unacceptably risky -- vever mind how effective it would be -- and so the administration finally decided in respect to Iran. Projecting power, with restraint and on request, into a tense political situation is possible, and the administration is doing it in Saudi Arabia.

Tougher demands on American policy than those posed in recent days can be imagined. Yet it is gratuitous and harmful to convey the impression that the United States cannot keep up the pace in the ongoing strategic competition of the Persian Gulf. It weakens the courage of friends, if not of ourselves, and it misleads adversaries. Politically, no doubt, things will be worse for us in Iran when the dust settles. But Iran will not have lost its interest in selling oil, and only to a point -- one affected in part by the American attitude -- is the American loss a Soviet gain. The Saudi monarchy is weakest in its feeble capacity to protect itself against outside marauders, and that is precisely the threat against which the United States can offer the greatest reassurance.

Force is an effective instrument to bulwark American diplomacy or, if necessary, to substitute for it. Not withoug some uncertainty, the United States is in the process of showing, we think, that it can usefully and responsibly bring force to bear.