OR SOME MONTHS prior to Iraq's invasion of Kuwait, American intelligence had been keeping an eye on one of the world's leading arms suppliers, Monzer Al-Kassar.

A multi-millionaire Syrian with multiple passports, he was being watched by Western intelligence services because of his known association with suspected terrorists and his role as arms supplier to governments and guerrilla forces around the world. Today, officials of several intelligence agencies say, he is perhaps the most successful private arms dealer in the world.

Global arms merchants such as Al-Kassar will always find rogue buyers like Iraq's Saddam Hussein. Tracking their tangled dealings yields vital information about the shadowy world of terrorists and despots.

Al-Kassar was expelled from Spain, his preferred base of operations, by pressure from the U.S. government in 1987, according to a U.S. intelligence official. Since then he has been shuttling around the world using Syrian and Brazilian passports. Last year he was spotted by U.S. intelligence in Budapest, Damascus and Kuwait.

It is one of the many ironies of the gulf crisis that Kuwait once hosted Al-Kassar, whom Western intelligence agencies consider most responsible for arming terrorist Abul Abbas and the terrorists controlled by Abu Nidal -- both of whom are now in Baghdad swearing to unleash a wave of terrorism against Saddam Hussein's enemies -- including Kuwait.

But in the global arms trade, almost every deal packs a potential irony. For example, of 50 countries that sold arms during the 1980-88 Iran-Iraq war, 28 sold weapons to both sides. Global military sales are enormous -- and largely beyond the control of mechanisms established by the United States and other Western countries to prevent the spread of mass weapons of destruction to the Third World.

The international arms trade only begins with multi-billion-dollar government-to-government transfers and sales. It also encompasses an intricate network of middlemen, companies and cutouts -- from the legitimate, like General Dynamics, to the shadowy, like Monzer Al-Kassar. The difficulty for all governments is controlling this vast network.

Iraq's case exemplifies the ambiguities of control. From the start of the Iran-Iraq war in September 1980, the world's arms dealers gathered like carrion to pick on the corpse of conflict. Before the war, the United States had branded Iraq as a state sponsor of terrorism and a tool of the Soviets. But once the war began, Iraq became the combatant of choice in official U.S. policy. In 1982, the Reagan administration removed Iraq from the list of those countries which supported terrorism and in 1984 restored full diplomatic relations. This was a clear signal to the Western world that Iraq was back in the fold.

According to the Stockholm International Peace Research Institute (SIPRI), Iraq had the highest military expenditure in the Middle East during the 1980s, peaking at $33.3 billion in 1984 -- about 30 percent of the country's gross national product. Even in 1989, Saddam still spent $15 billion.

Iraq received weapons from almost every arms-producing country in the world: artillery from Austria, armored cars from Brazil, aircraft from France and helicopters from Chile and Italy among others. Today, the U.S. Customs Service is investigating 40 cases of arms-smuggling to Iraq. Even late last year, after the invasion of Kuwait, Iraq actually sent machinery back to the United States for repair. The machinery allows Saddam to manufacture an impeller that helps shells explode in the air -- a device that will contribute to allied casualties if there is a ground attack against Kuwait.

Of greater concern is Saddam's chemical and biological warfare capability. Here, too, Saddam has managed to exploit weak control systems in the West to build the factories and buy the raw materials to make some horrifying weapons of war. Led by West Germany and France, European countries have supplied Saddam with all the raw materials he needs. He has built one of the most effective chemical and biological production facilities in the world, and no government has been able to stop this trade. The West German and French governments did nothing to stop companies from trading with Iraq. In Britain, an antiquated control system was no match for a sophisticated Iraqi underground purchasing network that made extensive use of dummy companies. While Saddam is a visible and painful reminder of how ineffectual controls against arms shipments have been in recent years, arms proliferation is not simply a question of what happened with that country. Chemical weapons -- the nuclear bomb of the Third World -- are cheap and militarily effective and offer grim international clout to underdeveloped countries. Twelve nations probably already have a chemical capability: Burma, China, Egypt, Ethiopia, Iran, Iraq, Israel, North Korea, South Korea, Syria, Taiwan and Vietnam, according to specialists who monitor global arms trafficking. These officials said 18 more countries have been trying to obtain chemical weapons and may have succeeded. On past history, most of these countries will succeed in getting a chemical capability with the help of Western companies that seek a profit and have little concern about how it is obtained.

In March 1985, Secretary of State George P. Shultz called for new efforts to curb the spread of chemical weapons. The Australian Department of Foreign Affairs took the initiative, hosting a meeting in Paris that June of representatives from Australia, Canada, Japan, New Zealand, the United States and the European Community. The Australian Group, as it is known, meets every six months, generally in Paris, and has drawn up a list of chemicals commonly used in the manufacture of weapons.

By September 1987, the Group had expanded to include Norway, Portugal, Spain, Switzerland and the European Commission. The representatives identified eight chemicals that now require export licenses from member states, and a further 30 were placed on a watch list that members hoped would give early warning of a country's intention to develop chemical weapons.

The Group is a useful initiative, but problems of verification threaten its chances of success. Governments can enforce a ban on the export of the eight key chemicals in the same way they can impose a ban on the export of mortars or rifles. But export controls on conventional weapons have proved only partially successful; and the same is true of chemical products. In addition, while conventional weapons are relatively easy to define in terms of export bans, most chemicals have a dual use in such peaceful pursuits as the manufacture of fertilizers. Effective controls would eliminate this elusiveness. Even so, the Group remains a toothless warrior because there are no sanctions that can be imposed on any country or government -- even a member of the Group -- that ignores its advice or turns a blind eye to a profitable private deal.

For example, at the same time that West Germany was actively participating in the Group, the Bonn government was being warned by both British and U.S. intelligence that the Libyans were building a chemical weapons plant at Rabta, 35 miles southwest of Tripoli. For more than a year, the Germans, along with the French, Italians and Japanese ignored evidence that companies were supplying Libya. Even when the United States went public with some of the evidence, the Germans continued to deny any involvement, and investigations were very limited.

The United States is now convinced that Libya has joined the chemical weapons club. The Rabta episode deeply frustrated the British and Americans: Although the intelligence information seemed clear and unequivocal to them, they had no way of compelling normally friendly governments to control the proliferation. As has often been the case in recent years, particularly during the Reagan administration, there was distrust among the Europeans of the U.S. information, a feeling that the excitable and bullying Americans were once again crying wolf.

Chemical weapons are, of course, only the start of the problem. As the allies have discovered in the gulf, the most powerful weapon seen so far in Saddam's arsenal is the Scud missile. While too inaccurate to be an effective military weapon with conventional explosive warheads, it has had a major political impact on the war and has caused terror among some Saudi and Israeli citizens. The Scud can carry chemical weapons; but as of yesterday, these have not been reported used. The combination of relatively cheap chemical weapons and ballistic missile proliferation has caused great concern to Western governments. Although ballistic missiles can be very expensive, a large number of countries, including Egypt, Argentina and Iraq, are trying to develop their own while others are simply buying their way into the club. According to SIPRI, at least 22 developing countries have active ballistic missile programs, while 17 have actually deployed such weapons.

What is particularly alarming about these figures is that every nation with a chemical and biological weapons program has also embarked on a ballistic missile program. It is clear that developing countries have recognized that ballistic missiles and chemical weapons are a far cheaper option than trying to buy or develop nuclear weapons.

As with chemicals, a new mechanism emerged in April 1987 known as the Missile Technology Control Regime. Seven nations (the United States, Canada, France, Britain, Italy, Japan and West Germany) signed the agreement to curb exports of equipment that might be used to develop missiles.

The signatories agreed not to export "complete rocket systems (including ballistic missile systems, space launch vehicles and sounding rockets) and unmanned air vehicle systems (including cruise missile systems, target drones and reconnaissance drones.)" Individual rocket stages, some guidance systems and arming, fusing and firing mechanisms also were to be barred from export.

The seven further agreed informally to share intelligence about any efforts being made by Third World countries to gain access to such technology. This is a useful start in an area of great concern to Western governments but it may well be too little too late to stem the spread of mass-weapons technology. And even as that effort takes shape, new weapons loom on the horizon that make action to control proliferation all the more urgent.

Genetic engineering, the new science of manipulating and cloning genes, can produce a new disease-resistant strain of wheat or a super-cow producing many gallons of milk a day. It might also produce weapons with a very specific effect on the body, such as making all troops in the front line suffer acute vomiting for precisely 18 hours. If such weapons can be perfected, developing or expansionist nations will see them as a cheap magnifier of military power.

In the aftermath of the gulf war, Iraq and Kuwait will both head out into the arms market, cash in hand, to try to replace the weapons that have been destroyed -- and the world's arms dealers will be ready and waiting to supply them. The most expensive solution will be to buy tanks, fighter aircraft and artillery pieces by the thousand. A more practical solution will be to invest in the technologies that allow them to make biological and biotechnology weapons. In its new and successful role as the respected leader of the free world, the United States must make sure that such ambitions are not realized. President Bush has said he wants to see a new world order emerge from the war. Part of that new world order must include tough new controls on weapons-producing countries to restrict proliferation. And for the first time, these treaties must include sanctions that make the lawbreakers pay a tough price.

The United States will have a unique opportunity to push for such controls once peace is restored in the gulf. Bush has won world respect for his uncompromising stand against Saddam. That strong position can bring together all the arms-producing nations to ensure that the next Saddam does not have such powerful weapons in his armory when he goes to war. Every allied soldier, sailor and pilot who dies in the gulf will underline the need for a new system.