IT IS A BIT foolish, given the evident fragmentation of political power in Tehran, to try to anticipate just how the various Iranian authorities will react to the position laid before them yesterday by Kurt Waldheim. The United Nations secretary general was bearing a resolution, passed 11-0 by the Security Council and supported by five Third World countries, calling on Iran to release the American hostages by Jan. 7 or face, not economic sanctions, but a council vote on sanctions. Who would be surprised if the Iranians decided, diliberately or by default, to call the council's bluff and force a sanctions vote? They might well figure that to get a strong vote the United States would have to offer a weak resolution. Anyway, no one really thinks that sanctions in themselves will bring the Khomeini regime to its knees, at least not in time to satisfy the dual American interest in getting back the hostages and salvaging national respect.

But this is not the end of it. There has been added to the Iranian crisis in recent days what you could call the Afghan factor: the deceitful invasion of Afghanistan by a large and evidently still-growing Soviet force that entered on the pretext of helping a beleaguered client regime, conspired to remove from power its head and to bring about his death, and set up a new client in Kabul. Correctly seeing the menace to themselves in this precedent of direct Soviet aggression outside the Soviet bloc, various Third World governments and personalities, especially from the Islamic world, have begun raising their voices in protest. Some strong drive will probably be launched soon at the United Nations to condemn the Kremlin.

But what about Iran? What country in the world has greater reason to take the new Soviet precedent seriously, right now , than Iran? It, too, shares a border with the Soviet Union: Soviet power is close by. It, too, surely has available, in the local communist party or elsewhere among the ranks of disaffected leftists and ethnics, a figure eager enough for power to sell out his country and provide a basis on which the same phony request for "fraternal aid" from the Soviet Union can be made. It, too, is enough of a strategic prize -- indeed, it's even more of a strategic prize than Afghanistan -- to tempt Moscow into a bold power play.

To be sure, some Iranians have already criticized the Soviet move into Afghanistan. But they, having scorned the words directed at them in the matter of the hostages, should be the first to consider that words are a flabby line of defense against real Soviet conspiracies and troop movements. They should consider that, by having isolated theselves on the hostage issue, they have cut theselves off from the very international company to which they would presumably want to appeal if the Soviet Union's current coolness to the Iranian revolution turned, as it easily could, to active menace. They might consider as well that it is the United States that, at least since World WAR II, has been the principal foreign champion of Iran's integrity and security.

In holding the hostages against the return of the former shah or against some American confession of historical wrongdoing, whatever it is, Iranians are wrestling with the ghost of the past.But they face, in the Soviet Union, a very real and dire threat to their current well-being. For Iranians who care about the future of Iran, can there really be a choice?