IT BECOMES increasingly difficult to evade the question of whether, if the sanctions and the military buildup and the diplomatic overtures continue to make no difference, the United States will go to war with Iraq. The Soviet Union, which knows Iraq from its long involvement and from its thousands of technicians still there, believes that the sanctions will tell in just two more months. That defines the time President Bush has left to persuade doubting Americans and allies that, in the event the Soviets are too sanguine, a forceful response is the next option.

You could say that outcome was implicit in the decision of 26 nations to dispatch forces to the Gulf after Aug. 2. Not to deliver when their bluff had been called, not finally to act against a clear-cut aggression in which a state had been wiped off the map: this would be a calamity to world peace and order. To leave a triumphant tyrant -- one possibly about to add nuclear arms to chemicals he has already employed -- largely in control of the region's stability and the world's oil would be a gilded invitation to the jungle. There are some circumstances in which, diplomacy having failed, arms will have to be tried.

But a decision to meet Iraq's force by force cannot yet be taken. The risks are immense, in possible casualties and battlefield reverses, in economic disruptions, in strains on the anti-Iraq alliance and in Arab backlash, in divisions at home. And the Bush administration has scarcely begun to share, as it must, its calculations on these several scores. The better it anticipates these matters, the more acceptable a military option will be to the American people and the allies, if it is ultimately required -- and the more attractive a diplomatic option may appear to Saddam Hussein as a result.

George Bush has an army and an alliance in place, but he has not established the domestic or international support requisite to moving confidently from the diplomatic to the military plane. Hence his diplomacy -- which is being exercised by allies -- is hobbled and his military option clouded. He has yet to provide a clear and consistent picture either of the present and future menace of Saddam Hussein or of the goals of American policy that might dictate a turn to arms. Mr. Bush cannot afford to lose the time he has apparently given the Kremlin and others to show what their diplomacy can yield. Unless he checks the drift, he heads toward the new year without either a good diplomatic choice or a good military one.