Anti-Sandinista guerrillas fighting along the Nicaragua-Honduras border are seeking significantly increased outside assistance to improve their supply lines and logistical capability and allow them to move their war deep inside Nicaraguan territory this summer.

Guerrilla spokesmen and informed foreign officials interviewed over the past several weeks in this country and Central America say such increased support, which would include heavier weapons and aircraft that would allow the guerrillas to receive supplies far inside Nicaragua, currently is under consideration by their principal backers in Washington and Honduras.

Despite repeated attempts over the past year, the guerrillas of the Nicaraguan Democratic Force have been unable to advance from their Honduran bases in any strength beyond a thin strip hugging the border. The guerrillas say it was the lack of support for a lengthy land and air supply line, which they contend they were promised but did not receive, that forced them to withdraw after their one major foray inside the country, last April in the north-central Nicaraguan city of Matagalpa.

"It took us 20 days to walk out of there," one spokesman said.

The guerrillas say they must establish a significant military presence farther inside the country, where most of the Nicaraguan population lives, to convince the U.S. Congress that they can be "winners," or at least "contenders" in their war to overthrow Nicaragua's leftist government.

Such an accomplishment, they believe, would give them and the Reagan administration an added argument in efforts to avoid a congressionally imposed cutoff of covert U.S. funds when the fiscal year ends Sept. 30.

The guerrillas' hope of expanding the scope of their activities against the Sandinistas is one of a number of indications that all of the major actors in the Nicaraguan war are undergoing a reassessment of their positions and preparing for an escalation in both the level of the conflict and the amount of territory it affects.

Current reports from Nicaragua and a recent visit to that side of the border area indicate that while they continue to await guerrilla attacks in the interior, the Sandinistas have begun preparing the north for a major invasion. This week, the Nicaraguan Foreign Ministry accused Honduras of sending its own troops across the border to help clear Sandinista minefields, and the government reportedly has moved heavier weapons to the area to supplement trenches and bomb shelters dug into the region last year.

At the same time, the Honduran Army announced yesterday it had sent 1,500 troops into the region on its side of the border this week to reinforce a small artillery unit and a patrol company permanently stationed there, The Associated Press and Reuter reported from Tegucigalpa.

The guerrillas thus far have posed little direct military threat to the Sandinistas, as long as their activities have been confined to the isolated northern border area.

At the same time, however, despite vast potential advantages in manpower and weapons--assuming the current level of guerrilla strength without direct outside intervention or stepped-up assistance--the Sandinistas have been unable to deal with them definitively.

Within the narrow geographic confines of the border war, the Sandinistas last month suffered some significant setbacks before driving the bulk of the guerrillas back into Honduras during their most recent offensive. Although they managed to repel efforts to take any of the major towns in Nueva Segovia Province, they lost at least temporary control of a number of small villages and strategic sites and still do not exercise complete control over a significant part of the border region.

The Sandinistas charge that the guerrillas owe their initial success in the recent offensive to artillery, mor-tar and rifle cover provided for their advance by the Honduran Army. The Honduran government denies this and has said that any increase of its own forces near the border is in response to Sandinista escalation.

What may be more significant in terms of Sandinista inability conclusively to drive out the guerrillas has been Nicaragua's reluctance to commit large numbers of regular Army troops or significant heavy weaponry to either the northern front, where fighting is heaviest, or to separate border battles with Miskito Indians in the northeast or in the extreme south, where former Sandinista fighter Eden Pastora is waging his own faltering anti-Sandinista war.

The Sandinista side of the war thus far has been fought primarily by reserve units mobilized in cities in the heavily populated west-central part of the country and brought to the front for several months of temporary duty under Army leadership.

This strategy appears designed partly to allow the largely untested reserves to gain combat experience, and to involve a large population segment in the battle in order to promote support for the government.

But Sandinista officials say the principal reason for leaving the Army in its garrisons is fear of leaving major military bases and population areas without protection against precisely the sort of attack the Democratic Force guerrillas now say they are organizing.

Nearly all the combatants on all sides of the current Nicaragua war, or at least their leaders, fought in the country's last conflict, when the Sandinista National Liberation Front guerrilla army overthrew the National Guard of Anastasio Somoza.

In many ways, each side is now fighting on the basis of lessons learned in the 1979 anti-Somoza revolution.

A number of high-level Sandinista officials interviewed recently in Managua recalled that one of the reasons they were able to win in 1979 was their ability to draw the best-trained and most-experienced of Somoza's troops to the far south of the country. Invading in force from across the Costa Rican border, they convinced Somoza they planned to establish a frontier strip of "liberated territory." This territory would then be declared "free Nicaragua," an entity which could be recognized and openly aided by other governments.

The National Guard quickly be-came bogged down in the south, where the Sandinistas could easily slip over the border to their extensive supply and training bases in Costa Rica with little fear the Guard would follow. The net result of National Guard concentration in the south was that the heavily populated central region was left under-defended, allowing other Sandinista units to infiltrate, mobilize and ultimately take control of city after city north of the capital.

The Sandinista commanders say they do not intend to be tricked at their own game and will not make the same mistake as Somoza. The National Guard-led guerrillas, for whom Honduras in the north plays the role that Costa Rica played in the south for the Sandinistas in 1979, say they learned equally the Sandinista lesson of distracting mainline forces while moving into the middle of Nicaragua.

What makes the current situation different, however, is that defenseless Costa Rica never presented a military threat to Somoza, despite numerous charges that the National Guard had entered or fired into Costa Rican territory in pursuit of the Sandinistas. As charges and countercharges between Honduras and Nicaragua have escalated, both sides have felt obliged to increase their border fortifications and the Sandinistas increasingly have had to reassess their strategy for dealing with war on several fronts at once.