A joint U.S.-Honduran military exercise of unprecedented scale is being planned here with the aim of intimidating Nicaragua's revolutionary government, according to government and diplomatic sources. But there is growing concern that it could accidentally touch off a real war between the Central American countries.

"It's certainly going to rattle their cages," said one man familiar with the operation, tentatively scheduled for December.

The U.S. Army, Air Force and Navy will participate in what are described as support functions that could involve several hundred American soldiers. U.S. initiatives in the planning have drawn some criticism from Hondurans involved.

Honduran troop movements are supposed to take place throughout the country, but these sources said the main action is to be around Mocoron -- the site of a new military base as well as a camp of more than 9,000 Nicaraguan Miskito Indian refugees -- in isolated eastern Honduras close to the Nicaraguan border.

The section of Nicaragua to the immediate south of the operation site is wracked by periodic fighting between Managua's troops and anti-Sandinista rebels, including Miskito Indians, allegedly supported out of Honduran base camps.

Usually reliable sources involved with the planning of the maneuver, which has tentatively been given the Miskito name of Ahuas Tara, meaning Big Pine, say a propaganda "smoke screen" will be an important part of the operation.

The Hondurans normally conduct military exercises twice a year, and a program of joint exercises with the United States known as "Falcon View" has been going on for years. But military spokesmen say that Ahuas Tara is new, and much bigger than those operations.

According to sources familiar with Ahuas Tara, planning for the operation began as a relatively modest variation on the regular summer maneuvers for August, which were postponed because of floods.

In the interim, the scope of the operation increased dramatically. The maneuver is expected to last about five days and consist of the simulated rescue of a large garrison surrounded by an enemy incursion. Nicaragua has expressed concern that the purpose is to prepare for an invasion or to provide cover for stepped-up operations by anti-Sandinista rebels.

A source who works closely with both the U.S. Embassy and the government suggested that there is growing resentment on the part of some Honduran military officers because of what they see as the increasing interference of American "civilians" or intelligence agents in the planning of the maneuvers.

"Honduras wanted to improve its armed forces. The civilians want to use the operation for other purposes. They want to make it a big thing, to send a signal to Nicaragua," said one Honduran official.

Sources here insist that the operation is not meant to be an incursion, but a substantial feint near the border to convince the Sandinistas -- as one official put it -- "that they will be finished" if they do not bend to the general line adopted by Washington and Honduras.

The Hondurans, even some who would like nothing more than to march on Managua, appear to have much less confidence than the Nicaraguans in Washington's support for such a war.

"We have studied your history," one Honduran officer told an American reporter, alluding to Washington's reluctance when it comes to committing money or men that would be needed to wage a war . "We have to wonder if the United States is serious here or just fooling around. We tend to think now that it is just fooling around."

Military sources here say that any invasion of Nicaragua would have to be massive and quick. "It can't be a pinprick," said a senior U.S. military officer. "If they the Hondurans do something they'll have to go all out. Nicaragua is going to be very strong in two years."

Despite an almost 10-fold increase in military aid to Honduras since 1980, Washington has not given this country the kinds of military resources that the Honduran Army feels it would need to mount a full-scale invasion.

This realization, according to military sources, has tended to diminish the ardor for "cutting out the cancer" of Nicaragua that many Honduran officers have talked about almost since the leftist Sandinista government took over there in 1979.

What has been created, in terms of conventional warfare, is a balance of power in which neither side has a clearcut advantage.

Nicaragua's regular Army is the biggest in Central America. By most estimates its size has remained at about 23,000 men and women for more than a year. The Honduran Army has about 16,000.

The relative strengths or weaknesses inherent in armored vehicles, in naval patrol boats and other factors are argued inconclusively, but the essential pattern has been for Nicaragua's strength to be in numbers of infantry and Honduras' in its Air Force.

The advantage Honduras held in air power with 15 French-design Super-Mystere jet fighters acquired from Israel several years ago has been largely neutralized by the Nicaraguans' acquisition of highly mobile ground-to-air rocket systems, diplomatic sources report.

As the war of nerves has escalated, both Managua and Tegucigalpa appear to have encouraged irregular forces and rebels to step up their activity. Anti-Sandinista rebel groups work out of base camps in Honduras. Cinchonero leftist guerrillas and other terrorist organizations in Honduras have connections to Managua.

The "counterrevolutionary" forces operating into Nicaragua, said one Honduran officer, also serve the purpose of probing Sandinista defenses. Each side officially denies that it helps subversives working against the other.

It is against this background that Washington has stepped up concrete military demonstrations of support for the Tegucigalpa government.

In July, the U.S. Air Force moved more than 900 Honduran troops to the new military base at Mocoron in a highly publicized operation. At the same time, four U.S. minesweepers paid courtesy calls on Honduran ports. In late August, the landing-ship dock USS Portland stopped at the port of Tela.

A senior U.S. officer here said the visit was "routine" and "there's no political reason for it," but added, "I guess the Nicaraguans had reason to holler, with 608 sailors and marines only 300 miles away."

The officer said that until recently there was at most one U.S. Navy courtesy call a year in Honduras.

The Sandinistas have said repeatedly they will not be provoked into an armed conflict with Honduras. Nevertheless, they prepare for such a contingency and reportedly have moved up large troop concentrations.

The balance is delicate and dangerous, raising calls for a negotiated solution from Mexico, Venezuela and other countries before a miscalculation or provocation leads to a war that could engulf the region.

According to sources familiar with awaited maneuvers, when Washington argued that the operation should be conducted in the western region around Choluteca -- where an invasion would move right into the economic heart of Nicaragua -- the Hondurans refused, reportedly because of the high population density there.

On a recent afternoon, things were quiet at the garrison of the Mocoron Task Force in the midst of remote pine barrens surrounded by marsh. A guard at the gate stood idly scribbling verse in a battered notebook: "Oh forgotten corner of Honduras, now filled with valiant soldiers . . ."