In just 10 days, the Persian Gulf crisis has escalated from a distant conflict to a global confrontation with profound military, diplomatic, economic and political consequences.

The confrontation threatens to become a protracted stalemate -- potentially the greatest challenge to American will since the Vietnam War. With virtually no warning, President Bush finds himself facing grave issues: how to safeguard hundreds of thousands of foreign nationals in Kuwait and Iraq; whether to risk thousands of U.S. military casualties to drive Saddam Hussein out of Kuwait by force; how to combat a foe with hundreds of tons of chemical weapons; how to avoid an open-ended and immensely expensive commitment that could drag on for months or years, and pull the U.S. economy into a recession.

The stakes have doubled and redoubled. Bush implicitly has suggested that nothing less than the existing world order is at risk; Secretary of State James A. Baker III apocalyptically warned Friday of "a new dark age" if Iraq's aggression goes unpunished. This showdown in the gulf, said Sen. David L. Boren (D-Okla.), "could very well determine the extent of American influence in the post-Cold War world."

From the U.S. standpoint, a quick and happy ending to Operation Desert Shield would mean relatively straightforward consequences: restoration of something like the situation that existed before Kuwait was invaded; a demonstration that the global community can make sacrifices to uphold international law; reaffirmation of the United States as the world's preeminent military and diplomatic force; enhanced stature for Bush as a statesman-warrior who speaks loudly and carries a big stick.

But as tens of thousands of troops and an armada of warships converge on the gulf, a happy ending does not appear imminent. U.S. officials believe that a long-term solution probably requires the removal from office of Saddam; for a man "backed into a corner," as Bush described the Iraqi leader Friday, that may leave no face-saving option but a bloody fight.

The global revulsion at Saddam's aggression was nearly unanimous, and the response it produced has been swifter than anyone might have expected. By getting the Soviets to join in the condemnation of the invasion, by rushing to the defense of Saudi Arabia and by winning mandatory sanctions from the United Nations, the United States and its partners have denied Saddam any political cover for his invasion and deprived him of any room to hide.

But his isolation now makes the prospect of finding a diplomatic solution remote. One official suggested that Saddam might try to bargain with his neighbor, Saudi Arabia, to reach a settlement. U.S. officials say they hope Saudi resolve has been strengthened by the international commitment of recent days, so the Saudis will be able to resist any temptation to make concessions, particularly on the issue of restoring the Kuwaiti government.

Now that he has achieved the status of international outlaw, dealing with him will be more difficult. "Let's say Saddam Hussein decided to call it a day and rolled back home. Then what? The next time, it's almost certain he would go for broke right away," said Paul K. Davis, director of strategy assessment for the Rand Corp. and a former Defense Department official. "Or what if this crisis somehow is resolved and in a number of years from now Saddam is still in power and has nuclear weapons? Both of those argue for trying to resolve things cleanly now."

But there may be no "clean" solution given the vast numbers of foreign nationals in Iraq and Kuwait, including about 3,500 Americans, against whom Saddam can take reprisals at any time. An effective blockade might strangle Iraq, but how would the United States and its allies react to televised pictures of thousands of starving hostages held in Iraq and Kuwait?

Already pictures have appeared on front pages and television screens of worried families tying yellow ribbons on behalf of detained relatives. The administration faces a potential hostage morass much more complex than that which undid the Carter presidency a decade ago. Bush seems determined not to be trapped by history, scrupulously avoiding the word "hostage" and vowing Friday to avoid "elevating the value of any citizen."

The large number of foreigners in Iraq and Kuwait may be a kind of insurance policy for Saddam, but their presence solidifies international support for the effort to isolate him. For example, the Soviet Union has nearly 9,000 citizens in Iraq and Kuwait; Egypt has 850,000; Britain about 4,000.'Be Careful Where You Go These Days'

Some U.S. officials fear that Saddam could launch a terror campaign against Americans abroad or even in the United States. Again, the president has tried to project a studied nonchalance without being flip. "I'd be careful where you go these days," he said two days ago. Having raised the stakes so high -- with talk of "a new dark age" -- the administration implies that the larger national interests involved outweigh individual interests.

This unanticipated confrontation developed so quickly, with U.S. officials scattered around the globe at the time of the invasion, that many issues now coming to the fore have not been thoroughly analyzed, including the long-term impact of a stalemate. Much of the administration effort in the last 10 days has gone into engineering a string of diplomatic victories, most recently the agreement by a dozen Arab League nations to send troops to Saudi Arabia.

This lessens the danger of the United States being perceived as an imperialist aggressor; but if war erupts, Americans seem likely to scrutinize the nationalities of the casualities to gauge whether American boys are dying disproportionately for oil that is more important to Germany and Japan than to the United States.

The timely effectiveness of even a universal embargo remains to be seen. A 1985 study published by the Institute for International Economics concluded that since 1914, economic sanctions had been used successfully 39 times and to little effect 69 times. "Iraq's wealth comes only from oil, and it is a food-dependent country," Sen. Richard G. Lugar (R-Ind.) said. "That leaves it in a state of comparative weakness. Sanctions on food and oil will cause grave damage to the economy of Iraq."

But many analysts believe that could take months, and some wonder whether economic pressure can force Saddam to alter his behavior. "The only thing we've got now is to see if the sanctions and embargo lead him to change," said a Western diplomat in the region. "It's hard to believe he's going to just get out -- look at how he swallowed Kuwait." This official worried about whether the global campaign to isolate Saddam would provoke him further, fueling his quest to be seen as an Arab superpower. "He's a big hero in much of the Arab world," the official said. "A lot of Arabs like him."

For now, about a quarter of Iraq's million-man army is digging in in Kuwait and southern Iraq with machine guns, artillery, tanks and rocket launchers for a self-described "life-and-death fight." The U.S. deployment, quickly expanding from a trickle to a flood, could reach 200,000 troops under some circumstances now contemplated by the Pentagon.

The logistical and tactical challenges are as daunting as the 12,000-mile lifeline to Southeast Asia a generation ago. From the experience of reflagging Kuwaiti ships in 1987, military logisticians know that some kinds of equipment wear out three times faster in the harsh gulf climate than under more temperate conditions.

Strategically, some U.S. analysts now suspect that Saddam, having missed the opportunity for an easy invasion of Saudi Arabia, may have decided not to pull the trigger first. If economic sanctions fail to produce the desired results, the United States and its allies could thus face the momentous decision of whether to take the offensive. Although Iraqi targets are considered vulnerable to air strikes, past experience often has shown that the only way to dislodge an entrenched, capable enemy is with a ground attack that typically requires a 3-to-1 superiority in numbers over the defender.

Also, U.S. Army war games have indicated that the United States would find it difficult to oust an invader from occupied oil fields (such as Kuwait's) without destroying the production facilities, a prospect reminiscent of the infamous Vietnam-era statement that "we had to destroy the village in order to save it."

One Army official observed, "We have to disabuse people of the notion it would be easy. There will be lots of casualties and lots of destruction. This would be a high-intensity war against a modern force with combat experience" -- a far cry from the U.S. military's most recent outings in Grenada and Panama.

Iraq's vast stocks of mustard gas and sarin, a chemical weapon developed from insecticide, are a sinister wild card. The Italian defense minister said yesterday that Iraq is moving large chemical stocks close to the Saudi border, although U.S. officials said the Iraqi intent is unclear.

The prospect that Iraq might attack U.S. forces with chemicals could force the United States to contemplate seriously the use of nuclear weapons for the first time in 40 years. Some members of Congress, such as Rep. Robert G. Torricelli (D-N.J.), say they believe the United States should make clear that the use of chemicals will be regarded as the "moral equivalent" of detonating tactical nuclear weapons.

How to fight against gas is a subject of constant discussion in U.S. ranks. "If Iraq goes chemical, I would hope we'd take it up a step," said one commander preparing to ship out for Saudi Arabia. "My particular response would be to see that Baghdad didn't continue to exist. . . . In the final analysis, dying is dying. But I've just been conditioned to believe that chemical warfare is unseemly and unfair."Commanders Recall Vietnam

Such statements reveal the seeds of frustration scattered through the U.S. military as it undertakes a mission that, at best, is uncertain and unpleasant. Military leaders -- brigade, division and corps commanders in the Army, for example -- served as platoon, company and battalion commanders in Vietnam. In many cases, their psychology has been deeply affected by the experience of fighting a war with ill-defined objectives and politically motivated restrictions on their use of force. Few want to repeat that experience.

Regardless of how this crisis unfolds, the U.S. economy seems certain to suffer. Independent analysts suggest that the military buildup will cost hundreds of millions of dollars a month and many times that if shooting begins. Who will pay remains an open and tricky question; the Saudis, for example, badly want to avoid the suggestion that they have hired mercenaries.

The impact on the domestic U.S. economy is showing up already in higher gasoline prices and airline ticket prices. The Labor Department has said that higher energy costs -- particularly at the gas pumps -- likely will drive up inflation. With the economy nearly idle now, many economists believe higher fuel prices will trigger a recession.'Peace Dividend' Among Casualties

Among other casualties, the "peace dividend" anticipated at the end of the Cold War may be diminished. Those determined to maintain U.S. military might have seized on the Iraqi threat as an argument against gutting the Pentagon budget. "Saddam Hussein, for all the bad things he did, may have done us a favor," Senate Minority Leader Robert J. Dole (R-Kan.) said Friday of Republican efforts to minimize 1991 defense cuts. "He sort of woke us up in America and woke us up in Congress."

Saddam also revealed the perilous fragility of the "post postwar" epoch, as Baker called it. For optimists, success in the gulf could provide a prototype for international cooperation in the future and -- given the demise of the Soviet empire -- ratification of the United States as the only true superpower. For pessimists, Iraq's adventure may be the first in a sequence involving heavily armed, rogue states bullying their neighbors without the restraints once imposed by a U.S.-Soviet rivalry.

In the balance hangs the Bush presidency. Edward J. Rollins, who served as Ronald Reagan's political director, said, "George Bush . . . doesn't need anyone to explain to him the risks to his presidency of sending Americans into a conflict like this." Bush last week said he is "not worrying" about whether the U.S. commitment in the gulf is open-ended. But that decision may not be entirely the president's to make.

"No one wants or needs a war, and there's no evident reason for one," said Davis of Rand. "Certainly everyone would be relieved if Saddam Hussein decided to retire in Geneva. But he's just not the type."

Staff writers Dan Balz, Ann Devroy, John M. Goshko, Al Kamen, Molly Moore and Patrick E. Tyler contributed to this report.