While the international spotlight has strayed from Central America, the struggle in that region has continued and even broadened, and a strong possibility continues to exist of new showdowns and crises ahead.

The Reagan administration, however, is breathing easier in the belief that recent tests have been surmounted and the United States and its regional allies have stopped losing the battle for Central America.

"Nobody is saying any more that the Salvadoran government is going to fall. Nobody is saying that Honduras is going to fall. The notion that the Nicaraguan revolution is going to sweep others in its path is gone," according to a senior State Department official.

In the view of this official and others, the past few months have seen a halt to steady erosion in the U.S. position in the region and to guerrilla momentum.

The officials do not contend, however, that the change in the flow of events has gone far enough to put the Cubans, their Nicaraguan allies and other insurgent forces to flight.

Washington officials, in fact, continue to forecast that Soviet Mig fighters will arrive in Nicaragua, probably transshipped from Cuba. Crates that Pentagon analysts believe contain Mig 17s, probably bound for Nicaragua, reportedly were sighted recently in a Cuban port, and officials said some 70 Nicaraguan pilots and ground personnel were still being trained in Bulgaria and Cuba to handle Migs.

The long-expected arrival of Mig fighters in Nicaragua would be "a major escalation" and unquestionably would bring a "a major response" from the United States, according to official sources. Nicaragua is said to have been put on notice that this would be the case.

The sources will speak only in the most guarded terms of the probable nature of a U.S. response.

Among the options known to have been under study are U.S. military action to destroy the Migs, a blockade or quarantine of Cuba and/or Nicaragua, tightening U.S. economic restrictions on those two countries, temporarily stationing U.S. airmen and warplanes in Honduras and Colombia, stepped-up supply of U.S. combat aircraft to friendly countries and a political drive on the Migs issue in the Organization of American States and other international organizations.

The importation of Soviet warplanes would be likely to intensify and spread the conflict in Central America. Even without this development, the struggle for the region seems to have broadened geographically in recent months.

Supporters as well as opponents of U.S. policy see the strengthening links between national battles as a tendency toward region-wide conflict. There is sharp disagreement, though, about who is to blame.

"It has been regionalized, by Castro and Nicaragua with the support of the Soviet Union," said a Pentagon policy maker. "It would be folly on our part not to think of the defense in regional terms."

New evidence of the regional link, according to State and Defense department officials, includes Costa Rica's expulsion late last month of three Nicaraguan diplomats on charges of participating in the July 3 bombing of an airline office in San Jose.

U.S. officials said Costa Rican authorities believed the bombing was part of a Nicaraguan plan to weaken that country through terrorism, kidnapings and other such acts.

Additional evidence of regionalization, according to an official here, arose from the seizure July 8 of a guerrilla hideout in a suburb of the Honduran capital, Tegucigalpa. An official cited reports that the hideout yielded clandestine radio equipment, Chinese and Israeli weapons, bombs of the type used in an attack on a Honduran power station, electrical workers' uniforms and documents.

According to this source, the evidence indicates that one function of the hideaway was to "coordinate logistics" from Nicaragua to guerrilla forces in neighboring El Salvador and Guatemala.

A U.S. official acknowledged that the United States was "helping Honduras to interrupt the supplies" from Nicaragua to the Salvadoran and Guatemalan insurgencies. This evidently is one bureaucratic rationale for the continuing covert CIA operations in the Honduran-Nicaraguan border area, recent joint U.S.-Honduran military operations there and stepped-up U.S. military assistance, including a decision to augment the Honduran Air Force with six A37 light attack planes.

The two-week, U.S.-Honduran "combined movement" involved U.S. pilots, mechanics, air traffic controllers and two U.S. C130 aircraft helping to transport a Honduran battalion to a new base just north of Nicaragua. Officials conceded that the operation might have had the practical effect of keeping the pressure on Nicaragua's Sandinista government.

A policy of continuing military and paramilitary pressure against Nicaragua is reliably reported to be part of U.S. strategy, although the administration does not publicly acknowledge it.

Nicaragua, in a diplomatic note delivered to the State Department early this month, protested the U.S.-Honduran maneuvers and charged that they "represent a clear and open provocation which appears to be aimed at causing an unnecessary war between Honduras and Nicaragua, with unforeseeable consequences."

The Nicaraguans also charged that "these maneuvers are taking place simultaneously with an increase in counterrevolutionary activities carried out against our territory by ex-Somoza guardsmen" organized as a regular army and equipped with "sophisticated weaponry, predominantly of U.S. manufacture." (The Sandinistas ousted Anastasio Somoza, longtime dictator of Nicaragua, in 1979.)

The diplomatic note went on to protest a July 24 "massacre and kidnaping of innocent victims in the village of San Francisco del Norte" just south of its border with Honduras and alleged attempts to destroy Nicaragua's petroleum storage facilities on July 11 and its only oil refinery on July 27.

Meanwhile, a major Honduran military sweep this summer along the Honduras-El Salvador border brought a protest June 27 from the general command of the Farabundo Marti National Liberation Front, the umbrella organization of Salvadoran guerrillas, that "the Honduran army has taken the first step in spreading the war thoughout the Central American region."

A Pentagon official said the Honduran troops went into "no-man's land" that is still disputed between Honduras and El Salvador, but he denied that the Honduran forces invaded clearly established Salvadoran territory. According to this source, the operation was coordinated by Honduran and Salvadoran armies to interdict main guerrilla supply routes and attack previously untouched guerrilla base areas.

A Salvadoran rebel leader, Eduardo Solorzano, was quoted as saying in early July that the joint Honduran-Salvadoran operations might require the Salvadoran guerrillas "to act in Honduran territory, not only in the frontier but in all of Honduras." The statement came at about the time of stepped-up terrorism and guerrilla activity in Honduras.

As U.S. officials see it, the insurgent movement in El Salvador is no longer growing, after the failure of the guerrillas to interfere with elections there March 28. Moreover, there are signs of internal disputes among guerrilla groups about their future course.

In Guatemala, the northernmost country in the region, the battle has not abated despite the coup March 23 that brought Gen. Efrain Rios Montt to power, backed by a group of young officers. U.S. sources said insurgent strength there seemed still to be growing, to about 3,500 full-time combatants.

Because of congressional opposition stemming from human-rights abuses, the United States has not supplied new assistance to Guatemala for several years, but the administration is now seeking to restart aid and to resume U.S. support for loans to Guatemala in international development banks.

Stephen W. Bosworth, deputy assistant secretary of state for inter-American affairs, has testified before a House banking subcommittee that "the record of the past four months, while not perfect, demonstrates that the new government has a commitment to positive change and new opportunity in Guatemala."

Based on this judgment, Bosworth said, the administration is accelerating disbursements still in the pipeline for Guatemala and "reallocating development assistance funds from projects canceled in other countries." Officials said the reallocation would probably be limited to $1 million to $2 million because of scarce funds.

Rep. Jerry M. Patterson (D-Calif.), chairman of the banking subcommittee that heard Bosworth, issued a statement opposing his views. "I think the State Department is making a mistake when it assumes that the Cubans are the problem in Guatemala," Patterson said. The real problems, he said, are poverty and oppression, and while Rios Montt's statements are positive, "the government's killings of civilians go on under the new state of siege."

The House Foreign Affairs Committee, meanwhile, has allocated $11 million for Guatemala in the administration-sponsored Caribbean Basin Initiative and approved $250,000 to restart the U.S. military training program for that country. An administration official said a modest beginning on new military aid or military sales to Guatemala, including access to military spare parts, was under consideration.

Finally, there is the question of U.S. quasi-military assistance to Costa Rica, which officially does not have a regular army and in the past has sternly rejected any offer of military aid. On a visit to Washington in June, President Luis Alberto Monge asked for security-related aid in response to growing internal strife and border trouble with Nicaragua.

"They'll get it," said a State Department official. "It will be very small."