The crisis in tiny El Salvador could shape President Reagan's policy toward Latin America and the Caribbean before Secretary of State Haig has time to formulate it. It is increasingly clear that the Soviets, through their proxy Castro, are supporting an early challenge to test the will and skill of the new administration as well as the new mood of the U.S. public opinion implicit in the November election results.

If the response is dominated by narrow views, we may well be on the way to a security setback. Reagan will be saddled with a Bay of Pigs or a mini-Vietnam. Such an entrance will bring glee to Castro and his Soviet mentors. On the other hand, if we draw on the lessons of the past and the realities of the present, this could be the turning point in the struggle for an area that is basic to our national security.

Our present predicament in El Salvador and the region in general is the result of several factors. One is underestimation of the strategic importance of the Caribbean and Central America because of the small size of the countries involved. Another is the naive policy of the Carter administration. Self-righteous moralism is not a substitute for security as a basis for development. The result has been a power vacuum -- eagerly filled by an expansionist Soviet-dominated satellite. Instead of development, we caused a capital overflow that has fueled the Miami real estate boom.

The setting for this struggle is societies, like El Salvador, in which expanded education, communications and transportation have created increased expectations among a growing population. At the same time, a total absence of energy resources has made both Central America and the Caribbean islands, except Trinidad, extremely vulnerable to oil price increases. Under such circumstances, the masses are easy prey to radical propaganda. The frightened members of the establishment, oligarchy -- or whatever one's ideological bent finds a satisfying label -- tend to resort increasingly to repression. They want to prevent what they logically perceive as a mortal threat to their interests. Castro and the Soviet Union prey like vultures in such an environment. However, in formulating response, it is important to keep in mind that, with or without the Castro-Soviet subversion, the structural stress in these societies will persist.

A realistic policy to protect our national interest in the region, therefore, should provide security, based on an approach that includes offensive and defensive components, and development that includes both growth and reform components. Such was the essence of our two previous successful efforts to contain Soviet overt or covert expansion: The Marshall Plan and the Alliance for Progress. Naturally, as in those two efforts, it will also require an equal commitment of national leaderships in the region.

In this last respect, there is a ray of hope for the Reagan administration. For throughout the Caribbean and Latin America there is a growing consensus that such an effort is needed to stem this new threat. Granted, there are those who would like us to pick up the tab, in lives and money, to preserve their priviledges. Others want us to subsidize the extermination of pro-U.S. authoritarians to be replaced by pro-Soviet totalitarians.

So far, Venezuela and Mexico, as well as Costa Rica, Barbados, the Dominican Republic and Jamaica, give indications of increasing awareness of the problem faced by the region. In El Salvador, the present leadership reflects this middle-of-the-road approach.

The implemenation of such a comprehensive policy embracing both security and development elements has been articulated very clearly by Jamaica's Prime Minister Edward Seaga. After leading his people to a dramatic victory of democracy over Castro-Soviet subversion -- which has not been sufficiently appreciated in the United States -- he has proposed a Marshall Plan for the Caribbean and Central America. So far, his proposal has not met with any response from the United States.

Such a broad strategy would provide the framework for the Reagan administration response in El Salvador. Regardless of the short-comings of the land reform effort there and the violations of human rights that unquestionably are taking place, the Duarte government embodies the security and development elements of the required response. To deny military aid to El Salvador because of human rights violations, ignoring that they are being carried out by both the left and the right, will be utmost folly. On the other hand, to encourage the notion that aid will be made available so the landowners can roll back the land reform and push hundreds of thousands of peasants to side with the left will be equal folly.

While the emergency in El Salvador is dealt with, the broader response to the idea advanced by Seaga should be formulated.

The offensive component of the security aspect of the policy should aim at making Castro's subversive efforts very costly to him. No military action against Cuba is needed. However, those fighting Cuban mercenary forces in Africa should be encouraged and assisted when consistent with other national security interests. The failure of Cuba's economy under Castro should be divulged by all available media. Economic concessions granted by Carter administration should be reviewed and canceled when appropriate.

Military assistance in hardware and training should be made available to national defense forces to boost their ability to resist subversive and terrorist efforts. This in itself will reduce the size of the forces willing to resort to violence as a means of social change.

The Organization of American States machinery for regional security and non-intervention should be used to provide diplomatic and legal underpinnings for such collective effort. It is important to avoid an effort that may be preceived as being U.S.-dominated. This may be helped substantially if a country like Canada, with a heavy interest in the English-speaking Caribbean, can be persuaded to join the Inter-American System as a full-fledged member. Brazil could also play a role since, as a donor, it shares with Mexico and Venezuela and concern for the security threat to the region. Nicaragua and Grenada shold be given a choice, but it should be clear that we will not help those who support threats to our security.

Parallel to the security umbrella provided by such an effort, the present Consortium for Caribbean Develoment, under World Bank aegis, could be expanded to include Central America. Furthermore, the consortium could serve to avoid adding a duplicate bureaucratic machinery and to accelerate implementation. An expanded program of bilateral U.S. aid could be added to reinforce our commitment. This, in turn, could also serve to ensure that our national security interests are given due weight when it is not possible to do so through multilateral mechanisms.