A step of progress

DIPLOMACY appears to have taken a measured step forward in Central America. The need now is to follow this with other steps, and without raising inflated expectations: The journey toward peace is long indeed.

Two elements make up this positive move. One is US Secretary of State George Shultz's trip to Nicaragua and meeting with that nation's leader, Daniel Ortega. The second is Mexico's decision to send a high-ranking representative to the June 1 inauguration of Jose Napoleon Duarte as El Salvador's president, evidently an indication of a Mexican decision to seek improved relations with El Salvador.

Almost at the same time, during his visit to Ireland President Reagan offered to negotiate a treaty barring the use of force in Europe, as originally proposed by the Soviet Union - provided the USSR in return would ''negotiate agreements which will give concrete new meaning'' to the principle of not using force.

A good deal of skepticism exists about the meaning of these actions and statements. Critics note that such steps toward diplomacy would likely have a positive effect on American voters in this election year. They add that some Republicans are concerned that Mr. Reagan is being harmed politically by a growing voter perception that he has been too confrontational in his approach to foreign affairs.

Also, they note that the United States would like to decrease the opposition in the Netherlands and elsewhere in Europe to the stationing of US missiles on European soil. In essence, the skeptics think the US moves may be only politics-as-usual.

We would prefer to think otherwise. We would hope that the Reagan administration considers that both need and opportunity exist for diplomatic initiatives to seek settlement of the various Central American strains - including those between El Salvador's factions and between the US and Nicaragua.

Similarly, the requirement exists for more direct communication between the US and the Soviet Union, to help decrease international tension and move toward a genuine peace.

At the same time it is important not to view the situation naively: Powerful antagonisms exist, and strength of purpose is required in dealing with each situation.

We would hope that the Shultz trip to Nicaragua is followed by other initiatives by the US and other nations of the Americas to bring peace to El Salvador, indeed to all of Central America.

Similarly, we would hope the administration takes initiatives to seek improved relationships between the US and other nations, including the Soviet Union. One essential element will be a constancy of approach, and an absence of immoderate statements, in order to build up trust among nations.