At this point in the Persian Gulf crisis the only outcome that can be ruled out is continued Iraqi occupation of Kuwait. Too much is at stake for either the United Nations or the United States to back down.

Meanwhile, the military forces gathering on the Arabian Peninsula will soon create the capability to push Iraq from Kuwait if it does not withdraw voluntarily.The question is not whether Iraq will leave Kuwait, but when and how.

The sheer size of U.S. military deployments to the Persian Gulf imposes a set of deadlines on President Bush. Despite official talk of merely defending Saudi Arabia, the full U.S. force, which will include elements of two armored divisions, will be capable of liberating Kuwait.

All units will be deployed by the middle of the month, but it is unlikely that the troops will be in position, well-supplied and acclimated to the harsh Saudi desert much before mid-November. That's when the military option becomes available.

Around March, the use of force will probably become a necessity rather than an option. Neither Bush nor the Saudis can sit on a force of this size forever.

Saudi officials worry lest a large U.S. military presence embarrass them during next year's "hadj," the annual pilgrimage of Moslems to Mecca, which begins in June.

By then summer heat will make military operations unlikely until the next September, leaving U.S. and other military forces sitting on their hands - and presenting targets to terrorists - through the long Saudi summer.

If Iraq has not withdrawn from Kuwait by early March, at the latest, the president will find it difficult not to resort to force.

War could come much sooner. Iraqi leader Saddam Hussein may not give the president the luxury of waiting. An Iraqi attack on Saudi oil fields would probably not succeed or cause much damage but might trigger war. So would terrorist attacks on oil facilities or U.S. forces.

Meanwhile, some officials in the United States as well as in the Middle East fear a diplomatic settlement that leaves Saddam with his army, chemical weapons, missiles and fledgling nuclear program all intact. They prefer a quick war that disarms Iraq as it liberates Kuwait.

War is rarely clean and quick, however, and unless he is guaranteed a clean, nearly bloodless victory, Bush has good reason to give diplomacy a serious chance.

There is little historical evidence to support the inflated view of air power voiced by former Air Force Chief of Staff Michael Dugan in the interviews that cost him his job.

No doubt air power is a principal U.S. advantage in this conflict. But air campaigns are almost always less effective and surgical, and more costly, than predicted.

Besides, only ground forces can seize and hold Kuwaiti territory. The good news is that seizing and holding territory is a classic military mission for which U.S. forces are well-suited; this is not Vietnam, where the military mission was never well-defined.

If military operations are focused solely on liberating Kuwait, they should not take more than a month or two.

But the bad news is that ground warfare is inherently messy and unpredictable. Murphy's Law was probably invented by an Army officer; ground force operations daily confirm the law's truth.

It is hard to imagine Army generals telling the president that he can liberate Kuwait without risking thousands of U.S. casualties, and this should encourage caution.

Remember, too, that this is and must be a multinational enterprise; the participation of Arab states like Saudi Arabia, Egypt and Syria, is crucial to strategic success. The United States cannot go to war unilaterally. All participants must agree to do so.

And military operations will necessarily be run through a multinational command chain that will take time to establish. On balance, these factors also encourage delay before striking.

For the moment, the military buildup in the gulf reinforces the embargo on trade with Iraq in encouraging a peaceful Iraqi withdrawal, since Saddam must know that if it comes to war he will lose much more than Kuwait.

It makes sense to give these pressures time to work. Diplomacy may not produce a neat solution to this crisis, but it is doubtful that war will, either. Besides, time will run out soon enough.

If diplomacy has produced no visible results by early spring, the military buildup will make war virtually inevitable.