When Theodore Roosevelt was president, he once pointed at a map of Central America and exclaimed: "These wretched republics cause me a great deal of trouble." It may not be long before Ronald Reagan, who is about to become the latest of Roosevelt's Republican successors in the White House, is having similar thoughts.

If Reagan is lucky enough to spend his first days in office without having to confront a world-class crisis in places such as Poland or Iran, Central America is likely to provide the first dramatic test of his administration's foreign policy instincts and the extent to which it will veer from that of the outgoing Carter administration.

On the surface, there seems little logical reason why that should be so. The six countries occupying the Central American isthmus are mostly tiny and of little inherent economic or strategic importance.

Yet over the last four years, the region has taken on a symbolic and political importance far beyond these substantive considerations. It has evolved into a sort of laboratory for testing the concepts -- primarily an emphasis on human rights and a determination to work with radical forces for change -- with which President Carter sought to gain influence in the Third World.

And these are ideas that Reagan singled out for especially harsh attack in the election campaign on grounds that they represent a desertion of traditionally dependable American allies in a vain attempt to woo forces that are a Trojan horse for Cuban President Fidel Castro.

Even within the Carter administration, powerful voices -- centered mainly in the Central Intelligence Agency, the Pentagon and its intelligence arm, the Defense Intelligence Agency -- agreed with Reagan's contention that Cuba, in league with the Soviet Union, is intent on extending communist influence throughout the Caribbean basin.

They argued that Washington's best response would be to reestablish its badly frayed ties with the military-dominated regimes of such Central American countries as Guatemala, El Salvador and Honduras.

However, the dominant say in determining policy went to the State Department, which argued that the status quo can no longer be sustained, that the United States has no choice other than to recognize that change is coming to Central America and that, for both practical and moral reasons, Washington must find ways of accommodating it.

These differing views were underscored arrestingly in a recent television exchange between Reagan's ambassador-designate to the United Nations, Jeane Kirkpatrick, and Patt Derian, the outspokenly controversial assistant secretary for human rights in Carter's State Department.

Referring to the situation in Central America, Kirkpatrick said, "If we are confronted with the choice between offering assistance to a moderately repressive autocratic government which is also friendly to the United States and permitting it to be overrun by a Cuban-trained, Cuban-armed, Cuban-sponsored insurgency, we would assist the moderate autocracy."

Derian's response was explosive: "What the hell is 'moderately repressive' -- that you only torture half of the people, that you only do summary executions now and then? I don't even know what 'moderately repressive' is. The idea that we somehow must stand closer to dictators -- people who are cruel to their people -- is absurd."

Nor was that the only occasion when Central America has disturbed the foreign policy transition between Carter administration officials, whose reformist ideas derive from the civil rights and antiwar movements of the 1960s, and Reagan supporters, many of whom are young neoconservatives who have waged four years of guerrilla warfare against Carter's Latin American policies with the fervor of crusaders.

Documents from Reagan's transition team at the State Department were leaked to the press to implant the impression that some of Carter's ambassadors in Central America were exceeding their authority by playing the role of liberal "social reformers" and have been marked for replacement. Two of these ambassadors -- Robert White in El Salvador and Lawrence Pezzullo in Nicaragua -- fired back publicly with charges that Reagan supporters were encouraging reactionary elements in Central America to resist change by promising them future U.S. support.

These flare-ups, plus the fact that one key element of the Central American equation -- the bloody civil war between rightists and leftists in El Salvador -- is nearing crisis proportions, mean that Reagan and his secretary of state-designate, Alexander M. Haig Jr., will have to give early priority to a strategy for the region.But, despite everything said during and after the presidential campaign, there so far is no real road map showing the precise direction they will take.

Haig has no knowledge or experience of Latin America, and he has yet to choose the assistant secretary for inter-American affairs and the ambassadors and other subordinates who will be responsible for devising and executing the policy. Speculation about the assistant secretary post alone ranges over a very wide spectrum of names associated with right-of-center views.

They include Pedro Sanjuan, author of the leaked transition report criticizing the Carter approach; James Theberge, a former ambassador to Nicaragua, and Roger Fontaine, a research scholar with the American Enterprise Institute. They also include outgoing Sen. Richard Stone (D-Fla.), who defected to the Republicans after losing his bid for renomination and who long has advocated a tough anti-Castro policy; retired Lt. Gen. Gordon Sumner, a former chairman of the Inter-American Defense Board who has the backing of Pentagon hawks, and John Carbaugh, a leader of the young Republican ultra-conservatives and an aide to Sen. Jesse Helms (R-N.C.), who will head the Senate's hemispheric affairs subcommittee in the new Congress.

While all have unimpeachably conservative credentials, they are by no means alike in their thinking or style of operation. As a result, a lot of the questions about Reagan's policy can't be answered until the key subordinates are chosen and the degree of their influence and authority defined.

An even bigger problem than personnel selection is the complexity of the Central American situation and the different difficulties it poses in different countries. As a Carter administration official says:

"If you're going to change direction down there, it's not a simple matter of flicking an on-off switch, as some of these people seem to think. It's more like an intricate organ keyboard, with each country a different key, and there are lots of different ways you can play them."

When Haig takes over, he will inherit policies that currently give priority to three countries. In each, the processes of violence and revolution are in different stages of development and different situations have to be confronted. They are:

Nicaragua, where a bloody civil war ended 1 1/2 years ago with the long dictatorial hegemony of the Somoza family being overthrown by the radical Sandinista Liberation Front. Although the present Sandinista-dominated government contains strong Marxist and pro-Cuban elements, the United States has approached it with cooperation and liberal financial aid on the theory that Nicaragua can be steered onto a democratic course that will mix socialism with some elements of capitalism and that will be nonaligned in foreign policy.

El Salvador, where a coalition of reformist military officers and centrist civilian politicians that seized power 15 months ago is being backed by the Carter administration in hopes it can carry out far-reaching reforms and reconcile the warring rightists and leftists. The recent murder of four American women missionaries -- an apparent sign of the government's inability to control rightist sympathizers in its own security forces -- caused Washington to suspend $5 million in nonlethal military aid, but it is continuing $20 million in economic assistance in hopes that the government can get a grip on the situation.

Guatemala, where a military-backed rightists government is struggling with leftist terrorists in a cycle of back-and-forth violence that has started to resemble what happened in Nicaragua and what is going on in El Salvador. U.S. policy has been to try and defuse the situation by prodding the armed forces to support reforms in exchange for a renewed U.S. military supply and training relationship.

Such policies certainly are light years away from the approach used by Theodore Roosevelt and other presidents of his generation to deal with trouble in the region. After living a while in Central America, the writer O. Henry described those turn-of-the-century methods this way: "The little opera-bouffe nations play at government and intrigue until someday a big, silent gunboat glides into the offing and warns them not to break their toys."

The era of "gunboat diplomacy" and its accompanying contingents of U.S. Marines is still vividly remembered and bitterly resented in Central America. Nicaragua's Sandinistas, for example, chose the name of their movement in pointed homage to Augusto Cesar Sandino, a martyred nationalist who led an insurrection against U.S. occupation in the 1920s.

A later Roosevelt, Franklin, finally withdrew the Marines and gunboats. But, in enunciating his famous "good neighbor policy," he laid the foundations for a new kind of status quo -- one that effectively put responsibility for keeping the region quiescent on local strongmen who, in exchange for American backing within their respective domains, could be counted upon to act as surrogates for U.S. interests.

In Nicaragua, the Somozas and their cronies ran the country much the way Frank (I am the law) Hague ran Jersey City. In the other countries, the cast of characters changed more frequently. But the pattern invariably was the same -- a clique of officers, landholders and businessmen ruling over rural plantation societies of largely impoverished and apathetic peasants.

For the most part, these systems were "moderately repressive" in the sense that Kirkpatrick appears to be talking about. Wholesale killings and imprisonment weren't required, since most people were disposed to accept the system and stay in line. When someone did cause trouble, he usually could count on being exiled rather than shot.

From time to time, some cosmetic bows were made toward democracy. (One country, Costa Rica, even succeeded in making the transition to a genuinely democratic system.) But, in most of Central America, the norm remained dictatorship and corruption at the top and seething poverty and backwardness below.

It was a system with which U.S. policymakers found little fault. In 1954, when a leftist government unexpectedly emerged in Guatemala, the CIA promptly arranged a right-wing military coup to restore the balance. Later, after Castro won power in Cuba and began providing arms and training to Central American revolutionaries, the specter of communism in the hemisphere deterred even such reformist presidents as John F. Kennedy from trying to interfere with the Central American status quo.

Now, after the activist interlude of the Carter years, there is great fear in liberal circles that the Reagan people envision some sort of updated version of that old system for Central America. Certainly that seems to be the implication of Kirkpatrick's talk about "moderate autocracy" and Reagan's own campaign cry: "Must we let Nicaragua, El Salvador all become additional 'Cubas,' new outposts for Soviet combat brigades? Will the next push of the Moscow-Havana axis be northward to Guatemala and thence to Mexico, and south to Costa Rica and Panama?"

Carter administration officials contend that if the Reagan people think they can cooperate with the old ruling elites to restore some semblance of "the good old days," they are in for a rude shock. For one thing, these officials note, the expectations of the Central American masses have risen too high for the region to be kept placid without far-reaching reforms of the economic, social and political order.

But, when the ruling classes have been challenged by domestic insurgencies to make such reforms, their response has been to switch from "moderate autocracy" to vicious brutality. That was the case a decade ago when Guatemalan authorities put down a communist guerrilla movement by murdering thousands of people on the merest suspicion of harboring leftist sympathies. It was the case with the Somozas, often cited as models of "benovolent despotism," when they were struggling to keep their hold on Nicaragua. And it is the case in El Salvador at the moment.

Reagan's principal aides have been quick to denounce killing and violence from the right as well as the left in Central America and to stress their understanding of the need for reform. But, as the Carter administration learned -- first through its unsuccessful attempt to promote a centrist alternative to the Sandinistas in Nicaragua and now through its struggle to prop up a center government in El Salvador -- it's not easy to control rightist forces convinced they are fighting for their lives and willing to justify any excesses in the name of combatting communism.

"For Reagan, the great potential trap is that his concern about Castro will lead him into an uncritical embrace of military dictatorship," warns a State Department official. "If the United States starts building up the Central American military again with arms and training, they'll take it as a green light from Washington to do as they please, and before long the president will be defending himself against charges of abetting the worst sort of brutality and murder."

Even if that prediction turns out to be overstated, a shift by the Reagan administration toward closer ties with the military regimes would have immediate wrenching consequences for Washington. It would be resented strongly by Latin America's democracies, in particular the two most influential, Mexico and Venezuela, which have shown a paternal concern for the Sandinistas in Nicaragua and which have been urging that elements of the more radical left be brought into the Salvadoran coalition.

At home, such a move could bring Reagan into collision with the Roman Catholic church, whose outrage at the murder of the missionaries and of Salvadoran clerics has caused it to speak out with increasing anger about the excesses of the Central American right. It even could be a source of friction in U.S. relations with Western Europe, where many governments, particularly those led by social democrats, have advocated cooperation with the region's leftist forces.

There are other immediate questions that the Reagan administration also will have to face: whether to continue financial aid to Nicaragua (the Republican Party platform opposes it); whether to resume the suspended military aid to El Salvador; whether to replace the current group of U.S. ambassadors in Central America, most of whom are career foreign service officers, with envoys more acceptable to the region's military and business circles.

Reagan aides insist that no decisions have been made yet about any of these matters. They also deny rumors that contingency plans are being drawn to possibly send U.S. forces to Central America, that attempts will be made to destabilize Nicaragua through economic pressure and covert action by the CIA, or that increased cooperation with Central American armed forces will be an uncontrolled license for human rights violations.

Still, the rhetorical tone used by the president-elect and his aides leaves no doubt that their first emphasis is on containing what they see as the threat of Castroism. How they go about doing that while seeking to correct the economic and social problems that generate Central America's turbulence will have profound effects on U.S. influence not only in that region but also in the rest of Latin America and ultimately perhaps those other spheres of global instability that collectively are known as the Third World.