TEGUCIGALPA, HONDURAS, JUNE 18 -- Nicaraguan Indians who oppose the Sandinista government have concluded an assembly in a remote part of Honduras with an agreement to forge a unified organization allied with the main army of Nicaraguan rebels, according to diplomatic sources.

The U.S.-sponsored assembly, attended by about 1,500 Nicaraguan Indians, decided to establish a unified Indian directorate and military command, the sources said. But the agreements appeared to exist largely on paper at this point, and it remained to be seen what kind of unity would materialize among the fractious Indian rebel groups.

The meeting failed to produce an agreement on who would head the unified military command or who would represent the Nicaraguan Indians on the directorate of a new rebel coalition.

A European diplomat said the assembly produced the "minimum" accord that could have been expected. "A unified military command doesn't mean much without an agreement on who will head it," he said.

According to a diplomatic source with access to reports on the meeting, which was closed to journalists, the delegates expressed support for the idea of resuming a military struggle against the Sandinistas. The Sandinistas alienated the Miskitos after coming to power in 1979, but the government has been trying to make amends lately through a program of limited autonomy.

The assembly, which began last Thursday and ended late Monday, agreed to set up a six-member directorate representing anti-Sandinista natives of Nicaragua's Atlantic Coast region, but participants only managed to agree on three members, the sources said. The three are Brooklyn Rivera, Steadman Fagoth and Wycliffe Diego, Miskito rebel leaders who have been bitter rivals for power and influence.

The remaining three places were to be filled by representatives of Rama and Sumo Indians and English-speaking black Creoles, but these groups were still undecided on whom to choose, diplomatic sources said. The Miskitos make up the great majority of Nicaraguan Indians, who, along with the Creoles, live in eastern Nicaragua, an area historically isolated from the Spanish-speaking western part of the country.

Rivera, Fagoth and Diego reportedly continued to confer after the official end of the assembly in an effort to pick a single Atlantic Coast representative for a new Nicaraguan rebel umbrella organization, the Nicaraguan Resistance.

The umbrella organization has one seat vacant on its directorate for an Indian representative. Miskito membership in the organization will formally ally the Indians with the Nicaraguan Democratic Force, the main rebel army that claims to field more than 15,000 guerrillas.

The Miskito unity agreement was put together under U.S. pressure to forge a single Indian rebel organization in order to share in a $100 million aid package for the Nicaraguan rebels, who are known as contras. The U.S. State Department, which took over from the Central Intelligence Agency in March as the lead agency in handling the Miskitos, is said to have arranged the assembly.

The U.S. government financed the meeting, even purchasing cattle to be slaughtered to feed the delegates at the remote refugee community of Rus Rus in eastern Honduras, diplomatic sources said.

Honduran military authorities prohibited reporters from covering the assembly.

Several hundred Indians reportedly trekked in from Nicaragua to attend the assembly. The participants were said to include about 400 armed guerrillas of the KISAN group, which is headed by Wycliffe Diego and is already allied with the Nicaraguan Democratic Force. Diego, a former Moravian preacher, enjoys the support of the CIA, sources said.

To counter what was seen as a show of strength by Diego, about 200 Honduran troops also were present.

The Honduran troops were posted at the site by the military commander of the eastern province of Gracias a Dios, who is understood to support Fagoth. Rivera is based in Costa Rica and heads a small, largely inactive guerrilla force.

The Miskitos say Nicaragua's Indian and Creole population numbers as many as 200,000, but the Sandinistas put the figure at about 80,000, according to an expert on the Miskitos here. Since fighting between Miskitos and Sandinista forces began in late 1981 amid rebel raids and, later, forcible relocations by the Sandinistas of Indian peasants, more than 20,000 Nicaraguan Indians have fled into Honduras.