THE United States faces a critical turning point in the short history of the Mideast crisis. On Thursday, as the first of 200,000 additional troops called into service by President Bush three weeks ago began arriving in Saudi Arabia, the United Nations Security Council passed by a vote of 12 to two a resolution authorizing "member states cooperating with the government of Kuwait...to use all necessary means" to enforce the withdrawal of Iraqi troops from Kuwait after January 15. It was a gesture of unanimity unprecedented in the Council's 45-year history.

The council vote theoretically indicates the readiness of other major powers such as the Soviet Union and the United Kingdom to join in a military action against Iraq. But it is is generally understood as expressing the willingness of these powers to allow the United States to deploy its sizeable Mideast force directly against Iraqi positions.

One reading of the council decision might be that the United States has now secured from the international community a mandate to launch a full attack after the 15th of January. This would be a regrettable misinterpretation of the actual case. The members of the Security Council are hardly united around the idea of American attack in six weeks time.

The passage of the Thursday resolution required weeks of special lobbying by Secretary of State James Baker, and even so, is carefully worded to reduce its severity as much as possible. The six weeks period of grace inserted into the resolution came at the request of the Soviet Union, and a direct reference to "use of force" was removed from a draft version by the United States to prevent a Chinese veto.

Baker noted on Friday that the intention of the resolution was to "bring about a peaceful resolution." It is widely speculated that the point of the resolution is to convince Iraq that the threat of multilateral attack is so tangible that withdrawal is the only viable option.

If a diplomatic solution to the crisis is reached in the next few weeks, then all will be well. But if Iraq calls the council's bluff, the United States will be faced with a crucial decision Assuming that Iraq's reaction to the swiftly approaching deadline is not to launch a pre-emptive attack, should America invade?

The answer is no.

THERE is a genuine need to defend the principles of national sovereignty and non-agression. The United States is fully supported in international law if it attacks now, with UN sanction, to restore Kuwait to its previous state of independence. Such action would be consistent, to some extent, with the doctrine of collective security upon which the United Nations is founded.

But armed intervention is never justified under UN principles if a peaceful alternative is available. It is on this point that any American or other ally faces its strongest challenge. Can the various terms of the Security Council's earlier resolutions--complete withdrawal from Kuwait, etc.--be achieved without resort to military confrontation? If the answer is yes, then the United States has no business launching an attack.

Or does it? Are there other interests that the United Nations has not yet articulated that the United States is bound to serve? Is the invasion so immediate a threat to American security that it cannot be allowed to wither slowly under the weight of international embargo? What rationale for attack might the U.S. advance?

There are several. One is that action is needed now to restore the vital flow of oil to the West. But this has ceased to be a serious justification. The daily output of Saudi Arabia and other nations has risen sufficiently to restore world production to its pre-invasion level. Non-Arab holdings are estimated to be sufficient for decades more at current consumption levels.

A second argument in favor of immediate attack is that if Iraq is not beaten back now it develop a tactical nuclear weapon that will irrevocably shift the balance of power in the region and perhaps lead to a nuclear war. But Iraq's obtaining a nuclear capacity is not an immediate theat. Certainly it is not sufficiently imminent to justify an armed attack if any other option exists.

And indeed one does. The international embargo, when truly supported by member nations, is the only weapon the United Nations should ever have to apply against a nation that is not actively engaged in a shooting war. The idea that the past four months of embargo had no effect is naive at best and deliberately misleading at worst. Even a completely secure operation could not expect to substantially undermine Iraq's ability to function so soon.

But after 12 months, 15 months, an embargo will indeed begin to "bite." If applied for long enough, the will of the Iraqis to resist will decline steadily, the chances of Hussein's overthrow will rise and the potential impact of a desperate Iraqi attack anywhere will be less and less. Withdrawal from Kuwait and submission to other terms--e.g. the dismantling of nuclear development projects--should follow with capitulation.

IN THE end, the argument against an armed invasion rests simply on the plausibility of a successful, long-term embargo. And the Security Council decision on Thursday shows how such an embargo could succeed. The council has not voted to authorize the direct use of force in this way since the beginning of the Korean War, when the permanent Chinese seat was occupied by Nationalist China (Taiwan), and the Soviet Union was temporarily boycotting the Council.

Support of this kind from the five permanent members of the council as they stand today is unheard of. Such unprecedented global support for a military invasion surely suggests at least one other thing: that President Bush can now expect extraordinary cooperation in an economic blockade that would rival the greatest castle siege.

It is expensive to maintain an embargo, particularly for a period of months or years. But it is far less expensive than a war, and it costs far fewer lives. For all the assurances that an American invasion would be a quick, devastating affair, there are a dozen analysts, military strategists and combat veterans who claim the opposite.

The risks of a protracted groundwar are unacceptable if an embargo could accomplish the same ends.

And the renewed application of economic pressure is clearly the option most favored even by nations that support the council ultimatum: neither the Soviet Union nor China are strongly supportive of American intervention. Nor are the American people clamboring for a massive military engagement. Public approval ratings will not drop precipitously if the President announces that rather than risk thousands of American lives to begin a confrontation that may continue indefinitely, he has elected to maintain an increasingly unbreakable international blockade.

THIS course of action does not aid the hundreds of American and other hostages who remain trapped in Iraq and Kuwait. How many of them will survive the severe hardship and possible hysteria that a successful long-term embargo might engender? It is possible that they will be reasonably well treated to maintain their status as "human shields"; it is just as possible that they will be used as leverage against American opinion in more sinister ways.

Does the United States have an obligation, separate from other considerations, to rescue its captive citizens, whatever the cost? Such a call has shades of jingoistic fervor; it also strikes a powerful chord. This is perhaps the hardest decision the United States must face. But it is arguably the only valid consideration. Saving the hostages must be a strong enough reason on its own.

Thomas Gewecke '91 is president of the Harvard International Relations Council.