PARIS, AUG. 14 -- The piecemeal approach taken by West European nations in projecting air and naval forces to the Persian Gulf has highlighted the problems they face in building a common defense policy and raised new doubts that they can react swiftly to future security threats in the absence of American leadership.

In contrast to the speedy U.S. response, foreign and defense ministers of the nine-nation Western European Union are scheduled to meet in Paris next Tuesday to coordinate their military efforts in the gulf, nearly three weeks after Iraq seized Kuwait and posed an instant menace to the vast Saudi oil fields on which much of Europe depends.

The WEU has emerged as the principal focus of attempts to build a common European defense because it incorporates the arsenals of Britain, Italy, West Germany and France, which is not a full military partner in the North Atlantic Treaty Organization. Recent NATO proposals to create a European multinational force that would relieve U.S. defense burdens in the post-Cold War era have made little headway because of serious political and technical obstacles preventing speedy response to the kind of crisis now unfolding in the gulf.

Besides the linguistic and logistical troubles that any multinational unit must overcome to be effective, NATO studies have noted that establishing a political consensus on what constitutes a security threat and then agreeing on proper action would take a dangerously long time in a fast-moving crisis. In the wake of Iraq's invasion of Kuwait Aug. 2, West European countries unanimously condemned the aggression and agreed on the need to impose sanctions through the United Nations, but unity on political assessments and military deployment has been a distinctly different matter.

Among the European allies, only Britain and the Netherlands have joined the United States in the multinational force defending Saudi Arabia. France has insisted on maintaining an independent command for its seven ships and 3,500 men being deployed in the gulf. Italy, Belgium and West Germany have so far declined to send any forces there but have offered the use of bases on their territory and have dispatched ships to the eastern Mediterranean to replace U.S. warships being sent from duty there to the gulf. Tonight, West Germany officials said that they are considering sending minesweepers to the gulf as part of a European task force, but the matter is still the subject of emotional debate in the country.

The tactical role, operational area and rules of engagement for European naval forces in the gulf are supposed to be determined at the WEU meeting next week, but there is skepticism that any effective coordination will be achieved at the European level, leaving the United States or perhaps a joint United Nations command to supervise the effort.

West European governments have unanimously cited Iraq's violation of international law as the the main reason for their adherence to the mandatory sanctions imposed by the U.N. Security Council, but a variety of political, diplomatic and historical motives seem to lie behind the different military postures they have taken.

By rushing to join the Americans in defending Saudi oil fields, Britain has seized an opportunity to invigorate the special relationship with Washington that has faded as President Bush sought to establish a more intimate alliance with a stronger, unified Germany. Moreover, Britain has cultivated a lucrative military partnership with the Saudis in recent years that is likely to be enhanced by its vanguard role in helping the U.S. shield them from Iraqi aggression.

West Germany has adopted a low profile in the current crisis, partly because it is preoccupied with the problems of reunification but because, like Japan, it is prohibited by law from deploying forces beyond what is needed for the immediate defense of the country. Asked at a meeting of NATO foreign ministers why Bonn would not be sending forces to the gulf, Foreign Minister Hans Dietrich Genscher replied bluntly: "Read our Constitution."

Even if the Constitution were altered and Germans were free to join the gulf buildup, the memories of Nazi expansionism could evoke apprehension even among their European allies. "The Germans are really in a 'damned if you do, damned if you don't' situation," said Francois Heisbourg, director of London's International Institute for Strategic Studies. "There would be an enormous outcry if they sent their forces to the gulf, but they still get criticized for not taking a more forthright stand."

France has refused to follow Washington's leadership in the crisis, not only by insisting on its independent military command in the gulf but also in taking exception to American and British vows to interdict all Iraqi shipping. French officials said their government has argued strongly against imposition of a blockade because it would be an act of war that would make its participants "co-belligerents" in any gulf conflict and that they would join in such action only with United Nations approval.

President Francois Mitterrand is also pursuing an all-points diplomatic crusade by sending special envoys to 24 countries to explain France's position and seek possible openings for mediation of the crisis. Foreign ministry sources said it is possible that a French emissary could soon fly to Baghdad to negotiate the safe passage of Western nationals trapped in Kuwait and Iraq when their borders were closed.