Col. Moammar Gadhafi's combination of outdated ideology and state-of-the-art weaponry makes him a threat to America's interests and Libya's neighbors.

The latest U.S.-Libyan clash - in which American F-14s shot down two Libyan MiG-23s over the Mediterranean - is another periodic and necessary reminder for him to curb his ambitions and trouble-making.According to the Department of Defense, the aerial battle took place during routine U.S. maneuvers when the Libyan planes threatened the American patrol over international waters.

Although the incident occurred 600 miles away from its new chemical-weapons factory, the Libyan action was no doubt related to a fear that the United States would soon attack the plant.

Ever since he took power in September 1969, just before his 30th birthday, Gadhafi has persisted in his megalomaniacal ambition to be the leader of the Arab world.

Gadhafi has repeatedly failed in his attempts to undermine or take over other states. Neighboring Chad, with French assistance, beat back his invasion after several years. His blatant and bullying interference in other parts of Africa has made him an unpopular figure, particularly when his promises of aid were never fulfilled.

Gadhafi has no real allies in the Arab world. Money and arms have been supplied to terrorist and guerrilla groups ranging from the Irish Republican Army to the Moslem nationalists of the southern Philippines, without any appreciable gains for either Libya or its clients.

If one considers only Gadhafi's lack of political victories or strategic gains, he is not a threat to the U.S.

But Gadhafi's activities do pose a serious threat because of his responsibility for terrorist deeds.

Terrorism. Along with Syria and Iran, Libya is the leading sponsor of state terrorism. It has supplied training sites, false documents, safe haven, weapons, money and transport for a wide variety of terrorists. During the last two decades dozens of murderous attacks would never have taken place if not for Libyan assistance and, in some cases, direction.

After a particularly blatant terrorist attack on a club frequented by Americans in West Berlin, the United States intercepted radio communications proving Libyan involvement. In May 1986, the United States retaliated with a bombing raid on Libya. The results were dramatic: A badly shaken Gadhafi virtually ceased all of his terrorist efforts.

This lasted about two years. But there were increasing reports that Gadhafi wanted to renew his activities, using terrorists from the Japanese Red Army - a group that would be harder to trace back to Libya.

Last April, the Japanese terrorists, probably acting in concert with Lebanese colleagues, attacked a USO club in Naples. Five people, including an American servicewoman, were killed. About the same time, a Red Army terrorist was arrested on the New Jersey Turnpike, apparently en route to bomb a U.S. target.

Libya has also been mentioned in connection with the bombing last month of Pan Am Flight 103 over Scotland. If there is firm evidence of Gadhafi's involvement in that crime, the U.S. would seriously consider retaliation.

Chemical warfare. A more immediate issue is the news that Libya has constructed, with the assistance of West German companies, a factory capable of making chemical weapons.

Gadhafi denied this accusation, claiming that the plant makes only medicine. But his hollow alibi underestimates the effectivness of American intelligence, including satellite surveillance of the installation.

Iraq's blatant use of chemical weapons against Iranian soldiers and Kurdish civilians has dangerously lowered the threshold for employing such weapons. Gadhafi is scarcely a responsible leader - he has long sought nuclear weapons - and the prospect of his having mustard gas or nerve gas is quite chilling.

While the Libyan leader offered to allow international inspection of the plant, intelligence sources reported the Libyans were moving the chemicals used in poison gas so that the plant would appear to be "clean."

The Arab-Israeli conflict. Gadhafi is one of Israel's most stubborn foes, and is trying to torpedo any progress on negotiations to resolve the Middle East conflict. He has opposed Palestine Liberation Organization leader Yasser Arafat's tentative moves toward moderation.

It can well be argued that Libya is an easy target for American military power. It is weaker than Syria or Iran, and it lacks the degree of Soviet and Arab support enjoyed by Damascus.

But Libya should be aware of that fact, and its very vulnerability should make it more cautious. Since Gadhafi refuses to act in even a marginally responsible manner, the U.S. will have to pressure him either to compromise peacefully or to back down in the face of force.

(Barry Rubin is a senior research fellow at the Washington Institute for Near East Policy.)