Our nation has engaged in many "gray area" conflicts where Congress has permitted and even supported military action by the commander in chief without providing specific authorization or formally declaring war. Ordering more than 400,000 American troops into battle to liberate Kuwait is not a gray area. It is essential, to comply with the Constitution and to commit the nation, that Congress give its consent before the president initiates a large-scale military offensive against Iraq.

At the heart of the debate that begins today on the floor of the House and the Senate will be a deeply felt difference of opinion -- not over the ends of U.S. policy in the crisis but over the means of attaining them. I continue to favor President Bush's original strategy -- economic sanctions, a continued military threat and patience.

1. Iraq is unique in its vulnerability to economic embargo. The international blockade has succeeded in cutting off almost 100 percent of Iraq's exports (mostly oil), stopped over 90 percent of all imports and reduced its GNP by an estimated 50 percent. Over time, experts estimate the Iraqi GNP would be down by about 70 percent, the country will be an economic basket case, and Saddam Hussein may be in jeopardy with his own people.

2. The economic sanctions are international and supported by virtually the entire world. A war -- no matter how successful -- will be 90 percent American and will be viewed as an American crusade by much of the Arab and Islamic world. When the war starts and the dying begins, the American people will have every right to ask, "Where are our allies?"

3. CIA Director William Webster has testified that sanctions will increasingly weaken Iraq's military power through shortages of spare parts and munitions and equipment breakdowns. In addition, the embargo is a very effective mechanism to impede Iraq's quest for nuclear weapons and sophisticated delivery systems -- which should be one of our continuing goals after any resolution of this crisis.

In early November, President Bush abandoned his strategy of liberating Kuwait by maintaining an economic stranglehold on Iraq. Rather than preparing for the long haul by planning a rotation policy for American forces deployed in the region, he directed a buildup of American forces to a level that could not be sustained and that reduced our ability to respond rapidly to unforeseen military contingencies in other regions.

A sanctions policy is not perfect but has to be weighed against the alternatives. To those who say that economic sanctions do not guarantee Iraq will withdraw from Kuwait and conclude we must go to war after Jan. 15 absent a diplomatic settlement, I reply: What guarantees do we have that a war will be brief and that American casualties will be light? If we fight, we can and must win. But no one knows whether a war will last five days, five weeks or five months. Our policy and our military planning cannot be based on an expectation that the war will be over quickly and easily. In large measure, the scope and scale of the hostilities, once begun, will be determined by Iraq's willingness to absorb massive punishment and fight on. An Iraqi military collapse is possible but cannot be counted on.

I would also ask, what guarantees do we have as to the aftermath of the war? Here, too, caution is in order. Has anyone in the administration begun thinking about what happens after we win? The president's declared goals include establishing stability in the Persian Gulf and protecting U.S. citizens abroad. Considering the wave of Islamic reaction, anti-Americanism and terrorism that is likely to be unleashed by a highly destructive war with many Arab casualties, it is difficult to conceive of the Middle East as a more stable region where Americans will be safe.

Doubts have been raised about the coalition's staying power. However, the United States possesses sufficient military power to enforce an oil embargo unilaterally if necessary. Moreover, as Adm. William J. Crowe Jr. testified: "I cannot understand why some consider our international alliance strong enough to conduct intense hostilities but too fragile to hold together while we attempt a peaceful solution."

If Congress authorizes the president to wage war or he initiates it on his own, what kind of war should be waged? I am afraid too many recall our most recent conflicts in bumper-sticker terms:

"Vietnam: long, drawn out -- bad;"

"Grenada/Panama: quick, decisive -- good."

The problem is that a war with Iraq will be far different than any of these conflicts. In preparing for and planning for possible war with Iraq, we must get beyond such simplistic analogies. Above all, we must play to U.S. strengths and exploit Iraq's weaknesses. Our strengths include our air power, our maritime forces, our ground force mobility and our ability to use our intelligence and technological capabilities for selective destruction of Iraqi targets.

If war comes, Iraq's fondest hope is that the United States will commit substantial ground forces to frontal assaults, thus giving Iraq a chance to inflict heavy casualties. Saddam's military leaders are not fools. They realize that they will lose any war with the United States, but entertain the hope that high U.S. casualties would weaken our resolve.

Are there military lessons to be learned from Vietnam? Of course. We should hit military targets with awesome power at the beginning of any conflict, as well as knocking out power and communications, electrical, nuclear and chemical facilities. At the same time, we should not "overlearn" the Vietnam lesson. We in America like instant results. We want fast food and fast military victories. However, our nation places a higher value on human life, especially on the lives of our men and women in uniform. Depending upon developments after the first wave of air attacks, a short war may be possible and may save lives. But we must avoid "instant victory" demands and expectations that could cause a premature and high casualty assault on heavily fortified Kuwait by American ground forces.

If war becomes necessary, we should not tell our military commanders to get it over with quickly no matter what. The order should be -- "Accomplish the mission with whatever force is required, but do so in a way that minimizes American casualties, even if it takes more time." Making continued Iraqi occupation of Kuwait untenable with air and naval bombardment plays to our strength. Rooting the Iraqis out with ground forces going against heavy fortification plays into Iraq's strength.

Finally -- a message to Saddam Hussein. In the next few days, you will hear an impassioned debate emanating from the U.S. Capitol. These will be the voices of democracy. Don't misread this debate. If war occurs, the constitutional and policy debates will be suspended, and Congress will provide the American troops whatever they need to prevail. There will be no cutoff of funds for our troops while they engage your forces on the field of battle.

President Bush, Congress and the American people are united that you must leave Kuwait. We differ on whether these goals can best be accomplished by administering pain slowly with the economic blockade or by dishing it out in large doses with military power. Either way -- you lose.

The writer, a Democratic senator from Georgia, is chairman of the Senate Committee on Armed Services.