Charges last week by Secretary of State Alexander M. Haig Jr. that the Soviet Union was "training, funding and equipping" the forces of terrorism have suddenly thrust the shadowy world of international terrorist activity into the front lines of U.S. foreign policy and into the middle of a bitter and escalating verbal duel with Moscow. p

A few days before Haig spoke, President Reagan had welcomed the American hostages home from Iran and promised "swift and effective retribution" against future terrorist acts, a pledge that also focused attention on improving U.S. abilities to combat terrorism.

Haig's remarks, linking Moscow to global terrorism far more directly than past administrations have, appear to be part of an attempt to broaden public perception of the Soviet threat to U.S. interests -- a threat customarily expressed primarily in terms of Soviet military power.

A State Department spokesman, pressed the next day to explain what Haig meant, pointed to Soviet support for the Palestine Liberation Organization (PLO) "whose members have often been involved in acts of terrorism." He mentioned Moscow's use of Cuba and Libyan surrogates as conduits for assistance to terror groups, Soviet support for national liberation groups "that have used terrorist tactics," and general Soviet advocacy of armed struggle to solve regional problems such as those in El Salvador and Namibia.

Spokesmanm William Dyess added the official opinion that if the Russians "clearly understand that their fostering of terrorism is going to be very important to our future relations, then I think they will take heed."

Behind the scenes, however, Haig's blunt charges have also stirred confusion and controversy among some West European dimplomats as well as some U.S. civilian and military officials.

Soon after Haig spoke, diplomats here inquired of U.S. intelligence contacts if Washington had new evidence of Soviet involvement with terrorists.

Sources say the Europeans were told U.S. intelligence files contain little or no hard evidence directly linking Moscow to the kinds of groups that traditionally have been branded as terrorist, such as Italy's Red Brigades, Japan's Red Army, offshoots of the Baader-Meinhof gang in West Germany, Armenian groups that assassinate Turkish diplomats, or even the Iranian militants that seized the U.S. embassy.

There is evidence of Soviet military, though not necessarily terrorist, training for some members of the PLO. The PLO, however, draws considerable political and financial support from many countries, including some such as Saudi Arabia and Jordan which are important to the United States and which view the Palestinians as insurgents rather than terrorists.

In the past, the United States has carefully refrained from branding the entire PLO a terrorist organization. Reagan came closest last Monday in an interview when he spoke of "the terrorism that is being practiced by the PLO." Previous administrations have described the PLO as an umbrella-type political organization of many elements, some of which use terrorism.

There is also evidence that the Soviets and their Cuban, Libyan and East German allies provide financial, military, political and advisory support for a variety of insurgencies and so-called national liberation movements around the world. However, a view also widely held in many western countries is that many of these movements or insurgencies in Africa or Central America are not primarily Soviet fronts -- though they receive Soviet aid -- but are born of complex economic, racial and nationalistic movements. Intelligence sources also suggest that Cuba and Libya frequently move on their own rather than at the Kremlin's direction,

Those who are privately expressing concern about Haig's frontal attack on Moscow on the terrorism question believe it poses two dangers to foreign policy.

By blurring the distinction between the more commonly identified terrorist groups and the more politically motivated insurgencies and liberation movements that may also use terror tactics, the United States risks alienating friendly countries, especially in the Third World, which do not regard these movements as either terrorists or dupes of Moscow. The second risk they see involves being imprecise with Moscow on such an emotional subject.

There is also concern that with its broad definition of terrorism, the new administration may run into the same problems with the Kremlin that the Carter administration did at the outset by confronting Moscow on human rights. While the human rights campaign may have put the Soviets on the defensive initially, U.S.-Soviet relations never really recovered and the Carter White House was vulnerable to charges of a double standard in not applying the same pressure to nations more friendly to the United States.

"What is one man's national liberation terrorist is another man's freedom fighter," says a U.S. diplomat, alluding to the insurgents fighting the Soviets in Afghanistan and previous U.S. support to factions in Angola.

Some U.S. military officials privately describe terrorism as more of a nuisance than a real threat to U.S. interests. They are worried that all the publicity now being accorded to terrorism and the increased effort to gather intelligence on terrorists will take manpower and money away from what they see as the real intelligence problem -- countering the growing Soviet network of covert operations and intelligence agents in this country and throughout the world.

There is also interest in the role that Haig's personal views and experience play in the new emphasis on terrorism and Moscow.

In June 1979, long before the hostages were seized in Iran, Haig unleashed a scathing verbal attack on the Soviet Union at a press conference in Belgium marking his retirement as the four-star general in charge of NATO forces. Haig spoke just four days after narrowly escaping an apparent assassination attempt by still-unidentified persons who detonated a bomb under a bridge as Haig's car was crossing.

At that time, Haig spoke of "virulent forces" seeking to promote change through violence and charged that Moscow and the "totalitarian regimes of the East" bear a large measure of responsibility for the international disease of terrorism and upheaval.

When asked for evidence that the East was linked to specific terrorist acts, Haig backed off slightly, saying, "I do not attribute any particular terrorist activity extent today in the international environment as directly traceable to the active leadership or management of the totalitarian regimes of the East, but rather point out the philosophical underpinnings of those regimes, and in certain instances activity undertaken by them."

Claire Sterling, an American journalist who has worked in Europe for 30 years and is the author of a soon-to-be published book called "The Terror Network," insists that there is "overwhelming evidence" to support Haig's accusations and that her book will lay it out.

In a telephone interview, she said, however, that pulling together the evidence is a difficult process and that Haig should really have been prepared to say more to back up his charges because his remarks could be used against the United States unless they are substantiated.

As for the apparent lack of U.S. intelligence confirming a direct link between Moscow and terrorist groups, Sterling argues that the direct links are limited and skillfully covered up and that the real connections are via surrogate and proxy forces.

Sterling calls the Central Intelligence Agency, which declined to grant her interviews, "the least informed and most timid of any intelligence service on this issue." Sterling says Europeans know more about it than the Americans but are reluctant to talk about it because it risks confrontation with the Soviets as well as with Middle East countries.

State Department officials say the search for new ways to improve U.S. antiterrorist capabilities has really just begun. In 1979, there were 293 major incidents of terrorism wordwide -- bombings, kidnappings, assassinations and hostage situations. About 30 to 35 percent were directed at American people or institutions, including the seizure of the embassy in Iran, the destruction of the embassy in Pakistan and an attack on the embassy in Libya. In the first eight months of 1980, there were more than 500 major incidents worldwide.

Between 1974 and 1979, the State Department spent some $200 million on finding ways to limit access to embassies and prevent their seizure. Last year, $41 million was pumped in to enhance security at the highest-threat posts. Thus far, State has surveyed 18 such posts and will look at another 18 in the next six months.

The idea is to develop better control points at the perimeter of the installations and to provide more effective "safe havens" within the building. These are rooms that can hold large numbers of people and be sealed off against attackers while awaiting help from local government forces. The safe haven in the embassy in Islamabad, Pakistan, held 130 Americans for some 5 1/2 hours and was crucial in avoiding a high death toll during the November 1979 attack.

Also being looked at are ways to store classified information in other than paper documents so they can be speedily destroyed if necessary. State officials estimate that, all told, it may cost another $200 million over the next five years to make such improvements.

Also being reviewed are the procedures under which U.S. Marine guards can fire on attackers. As of now, the basic decision on use of lethal force is made by the ambassador or senior Foreign Service officer present, unless an individual guard faces an immediate threat to his own life.

If the United States is to reach out overseas with military force to squash hostage-takers or hijackers, the core of the existing capability lies with the few hundred commandos of the Army's top-secret "Delta Team" headquartered at Ft. Bragg, N.C. This is the group that attempted to carry out the Tehran rescue but never got a chance to show their stuff because the mission was aborted in the desert by helicopter and aircraft problems.

Those familiar with the commando unit say that it is equal or superior to any group in the world and enjoys excellent working relationships with elite British, French, West German and Israeli units. It remains to be seen, however, whether the men who pull the strings in the White House and Pentagon can manage to get these forces to the scene without the kind of confusion and eventual calamity that befell the Iranian rescue mission.