Top-level Reagan administration envoys will be carrying messages to Central America over the coming week. Two of the main aims will be to probe for signs of compromise from Nicaragua and to make a further effort to curb the death squad activity in El Salvador.
Vice-President George Bush and Langhorne A. Motley, the US assistant secretary of state for inter-American affairs, will make a stop in El Salvador on the return leg of a visit to Buenos Aires for the inauguration on Dec. 10 of Argentina's President-elect, Raul Alfonsin.
State Department officials say that one aim of the El Salvador stopover will be to show that at the highest levels, the Reagan administration is concerned about killings by right-wing death squads. The killings have led to sizable congressional cuts in aid to El Salvador.
At the same time, Richard B. Stone, President Reagan's envoy to Central America, will travel to the region and consult with representatives of the Contadora group of nations - Colombia, Mexico, Panama, and Venezuela - which are attempting to find a solution to Central America's conflicts. At some point in his tour, Mr. Stone is expected to stop in Nicaragua to determine in more detail what recent conciliatory gestures from the Sandinista leaders of that country might mean.
State Department officials say that the United States does not want to get into bilateral negotiations with the Sandinistas but will leave negotiations over a settlement to the Contadora group. The group's foreign ministers are expected to meet in Panama Dec. 15-16.
But Stone clearly has a lot to talk about with the Sandinistas. He met recently with representatives of five armed Nicaraguan rebel groups, more than one of fighting them with support from the United States. These groups differ on many points, but all of them expressed an interest in a dialogue with the Sandinista leaders. In return for a meaningful dialogue, they say, they would be willing to cease fighting. The Sandinistas have so far rejected the idea of such a dialogue.
Last Monday, Secretary of State George Shultz made the administration's first authoritative and positive statement concerning recent Sandinista gestures, which have included an announcement of plans for an election. Mr. Shultz said, ''What we want is for a reality to be put behind the rhetoric. And so, naturally , we want to probe and find out what is there.''
Some of that probing is to be done through contacts with the Contadora group, some through US Ambassador Anthony Quainton in Nicaragua, and some, of course, through Ambassador Stone.
State Department officials say that the Shultz statement and the probing are supported throughout the administration and do not just represent a State Department approach. Some congressional critics suspect that the State Department is more interested in negotiating a Central America settlement than are some top officials in the White House and Defense Department. But officials say that ways of easing the pressure on the Sandinistas have been considered, should the Sandinistas' conciliatory rhetoric produce results. One State Department official said, for example, that the US would consider lowering its presence in El Salvador and Honduras, if the Cubans withdraw from Nicaragua, taking with them their military and security advisers.
The official further said that no matter what ''hard-liners'' in the Reagan administration think or say, if the Sandinistas follow up in a meaningful way on their announced plans for elections and other liberalizing measures, the administration will be forced to respond. State Department officials estimate that there are 7,000 to 8,000 Cubans in Nicaragua, with 2,000 being military advisers and security personnel. Many of the Cubans are teachers and medical personnel who are said to have had military training. The Cuban government has said that the American figures are much too high.
A number of Cubans are reported, meanwhile, to have left Nicaragua recently, but State Department officials say that some of them appear to be teachers going on an annual year-end break.
Officials attribute the recent conciliatory gestures from Nicaragua to a variety of pressures - from the US, from US-supported rebels, from Nicaragua's neighbors, and even from Western Europe, where there has been some disillusionment with the Sandinistas. One form of pressure has been US military exercises off the coasts of Nicaragua and in neighboring Honduras. Another has been the impact of the Grenada invasion.
Some 4,000 to 5,000 US Marine and Army troops have been participating in military exercises in Honduras since last August. The current phase of the exercises is to be completed by the end of February. But that does not mean an end to the US military presence in Honduras. Additional exercises are being considered.
''The Honduran government likes having us there,'' said one official.
Defense Department officials would like to provide both Honduras and El Salvador with additional military equipment. One of Honduras's main strengths, its Air Force, is described as ''aging.'' Officials say that the Salvadorean Army needs more training and more helicopters.
But in the case of El Salvador, unhindered right-wing death squad activity has cut deeply into congressional support.
In a column published Thursday in the Washington Post, Rep. William S. Broomfield, a Republican from Michigan who is the ranking minority member of the House Foreign Affairs Committee, issued a stark warning to El Salvador.
''It is time to tell the truth about the death squads,'' wrote Broomfield. '' . . . First, I am amazed that the government of El Salvador has yet to stop these killings. Second, if more senseless murders continue, congressional support for that government will disappear. Aid will be cut. El Salvador will be on its own to fight the extremists on both ends of the spectrum.''