Americans, it is said, lack the patience for long wars -- which is why President Bush needs to pull out all stops to defeat Iraq as quickly as possible.

My own notion is that it isn't long wars, but ambiguity, for which Americans have no patience -- which is why the president needs to start looking for ways to end the fighting, or at least limit it to its present aerial phase.

The record suggests that Americans have plenty of stamina for war when the threat is evident and the objectives clear. Domestic opposition was not a factor in the two world wars. Even in the far less clear-cut case of Korea, there were no organized demonstrations against U.S. involvement. But by the time we were well into the Vietnam conflict, the ambiguities overwhelmed us. We were having difficulty distinguishing between Viet Cong, the enemy, and the South Vietnamese, our ally. We were finding it increasingly difficult to discern any objective for continuing the fighting, save to redeem the deaths of the thousands of Americans already dead.

Vietnam presented another troublesome ambiguity that has relevance for the present situation. Many Americans found it impossible to oppose U.S. involvement in the war without hoping for American defeat. For a short time, the anti-Vietnam protesters were simply urging America to find a pretext for ending the fighting. By the end, we were hearing chants of "Ho, Ho, Ho Chi Minh; Viet Cong are gonna win." If this war drags on, with America as the insatiable aggressor, don't be surprised to see President Bush transformed into the international madman and Saddam Hussein (at least in some American circles) into some sort of peasant hero.

For all the president's insistence that Iraq won't be "another Vietnam," that seems precisely where we are headed. We have the same vagueness of threat and purpose that plagued us in Vietnam, and we have the same disappointment that our sophisticated war machine has been unable to break the will of a relatively primitive opposition.

Now as then, military experts are touting the necessity of a ground war to achieve our objectives -- whether merely to drive the Iraqi forces out of Kuwait, to eliminate their capacity for further mischief or to kill Saddam.

Maybe it would work. Maybe our high-tech capability would be as effective on the ground as it has been in the air. Maybe there would be mass desertions by disillusioned Iraqi soldiers. Maybe the combination of encirclement of the dug-in Iraqis and the severing of their supply lines (the Ho Chi Minh trail?) would deliver an allied victory.

But maybe it wouldn't. Given the almost unavoidable toll in American lives and American patience, it seems a poor gamble.

There is another problem with the strategy Bush apparently has in mind. His carefully built alliance is terribly shaky. Many of the Arab leaders who joined the coalition understood themselves to be joining a defensive force. It's one thing to defend Saudi Arabia against an Iraqi attack, quite another to participate in an offensive war that pits Arab against Arab. It's also well to remember that the coalition is an alliance of Arab leaders, each with his own limited agenda, not of Arab populations, who will have no stomach for leaving Israel as the undisputed power in the region.

If Bush doubts the patience-in-war of the American people, what must he think of the staying power of the Arabs, so vital to the alliance? I hope the president is smart enough to continue the aerial bombardment for a few weeks more and then announce that we have adequately reduced Iraq's ability to fight, done sufficient damage to its supply lines and eliminated enough of his capacity for massive destruction that we can now withdraw to our defensive positions and wait for the international embargo -- remember the embargo? -- to work.

Nor need that be the declare-victory-and-get-out fiction proposed by the late Sen. George Aiken as a solution in Vietnam. I never understood the administration's insistence that the sanctions weren't working in the first place. If it meant that babies weren't starving to death for want of milk, who could have wanted them to work? But if it meant destroying Iraq's economy and its ability to rearm, it's hard to imagine that the sanctions wouldn't have worked eventually.

True, embargoes never are fully effective, and there's always some arms merchant willing to do business with any tyrant. But not on credit. Keep Iraq from selling its oil -- its sole commercial product -- and success would be all but certain.

For the time being, Bush has the backing of the overwhelming majority of the American people, including those who, as I did, wished he had tried harder to avoid war. But if the president leads the allied forces into a ground war, with its attendant casualties, he could find himself stuck with what he is sworn to avoid: another Vietnam.