Even as the United States increases pressure on Nicaragua, the two adversaries are exchanging faint signals which, if reinforced, could point toward peace rather than war.
Reagan administration officials say that it is still too early to assess the full significance of Nicaragua's offer to participate in regional talks on its problems with neighboring Honduras. Some experts fear that the current border fighting could lead to a full-scale war between US-backed Honduras and Soviet- and Cuban-supported Nicaragua.
But the reaction in both the White House and State Department to the negotiating offer made by Daniel Ortega Saavedra, Nicaragua's junta coordinator, was cautiously positive, and that is something new.
''It's the first time the Sandinistas have come through with something that could be viewed in a moderately positive light,'' a State Department spokesman said. ''Parts of it are certainly in line with what we've been saying.''
Another administration official pointed out, however, that while Mr. Ortega had renewed a Sandinista offer to negotiate a halt to the flow of all arms by any nation to El Salvador, there was no clear proposal as to how to verify such a halt. The US has been trying to get Nicaragua to stop shipping what it charges are significant quantities of weapons and ammunition to the guerrillas in El Salvador.
One administration official suggested that Ortega's motive in making a new negotiating offer may be merely to appear responsive and not to negotiate seriously.
''This is just a propaganda trick,'' says Adolfo Calero Portocarrero, a member of the political directorate of the Nicaraguan Democratic Forces (FDN), a CIA-supported movement fighting the Sandinistas in the north of Nicaragua.
''To make his new offer believable, Ortega should start by fulfilling the offer he made back in 1979 to the Organization of American States,'' says Mr. Calero, referring to the period leading up to the resignation of the late Nicaraguan President Anastasio Somoza Debayle and the takeover of the revolutionaries. ''The Sandinistas promised the OAS pluralism, democracy, justice, and free elections. What happened to those promises?''
In a telephone interview, Calero said the FDN forces ''hope within the next few days to achieve something really spectacular'' on the military front in Nicaragua. Other FDN spokesmen had earlier asserted that the FDN might launch new attacks on or around July 19, the fourth anniversary of the Sandinista overthrow of Somoza. They hinted that the actions might include attacks in Nicaraguan cities, designed to spark an urban insurrection.
In an anniversary speech made in Leon, Nicaragua, on Tuesday, Ortega declared that a Nicaraguan decision to enter into negotiations was designed to end ''excuses used against Nicaragua,'' which he asserted have blocked regional peace talks. Reagan administration officials said it would now be up to the four countries of the so-called Contadora Group - Mexico, Venezuela, Colombia, and Panama - to consider Ortega's proposal and see if it can be built upon when the group holds another meeting at the end of this month.
Previous to this, Nicaragua had insisted that its problems with Honduras, the base for the FDN rebels as well as for dissident Miskito Indians fighting the Sandinistas, be dealt with only in separate bilateral negotiations with Honduras and the US.
In his speech, Ortega called for, among other things, a freeze on all arms shipments to El Salvador, a lifting of the economic sanctions the US has imposed on Nicaragua, and a halt to the use of foreign territory to attack other nations - a clear reference to the use of Honduras by the Nicaraguan rebel forces of the FDN.
Ortega's speech came shortly after it was disclosed in Washington that the US was planning to mount two large military exercises in the region, one of which would include an aircraft carrier battle group. An administration official said the intention was to show the Nicaraguans and their Cuban supporters that the United States ''has the capability to operate in the region and has an interest in the region.'' But he added that the show of force was also meant to bolster the Salvadorean government and other friendly governments in the region which need to be reassured of American support.
Congressman Michael D. Barnes, a liberal Democrat from Maryland who is chairman of the House subcommittee on hemispheric affairs, said the US ought to assume that Ortega's speech is ''something real'' and follow up on it by encouraging the foreign ministers of the Contadora group to pursue it. He also suggested that the US demonstrate its goodwill by calling off the military exercises it has planned for the region.
Mr. Barnes has been named by House Speaker Thomas P. O'Neill Jr. to serve as a counselor to President Reagan's new bipartisan commission on Central America, which is to be headed by former Secretary of State Henry A. Kissinger. Barnes was critical of Reagan's appointment of Kissinger, because, he said, Kissinger was a controversial figure who might be unable to achieve a consensus on Central America policy.
''Henry Kissinger stirs things up rather than calms them down,'' said Barnes, who added that it was unfortunate that the 12-member commission did not include anyone whom he believes is knowledgeable about Central America.