A top leader of Nicaragua's Indian rebels has mounted a campaign to seek separate peace talks with the Sandinista leadership, despite what he describes as opposition from the Reagan administration.

The effort, by Brooklyn Rivera of the Misurasata insurgent group headquartered here, also aims at enlisting broad support from Indian refugees and fighters under the influence of another Indian rebel organization, Misura, headquartered in Honduras under the more conservative leadership of Steadman Fagoth.

Signs of interest in the peace initiative have raised the possibility that Misura might reduce its important military role in fighting alongside the Nicaraguan Democratic Force, the main rebel organization in a U.S.-backed guerrilla war against the Nicaraguan government.

Partly for this reason, Rivera said, the United States has discouraged and sought to block his attempt to unify Indian groups behind the idea of negotiations with Sandinista leaders to seek strictly Indian peace objectives.

More than 20,000 Miskito, Rama and Sumo Indians from Nicaragua's northeastern wilderness have fled to Honduras since the Sandinista government came to power in 1979 and sought to force its own form of revolutionary organization on the Indians' tribal ways. The Indians have formed a manpower pool for Fagoth's several thousand Misura guerrillas who, along with Rivera's smaller forces in the south, have hit hard against Sandinista Army units along the country's steamy Atlantic coast.

Armed with encouragement from the Indian elders and some Honduran officers, Rivera traveled to Nicaragua last month and met with Daniel Ortega, now president, and other Sandinista leaders. With special permission, he also toured the remote Atlantic region, which used to be home to about 90,000 Indians leading lives largely untouched by Nicaragua's dominant Spanish culture.

Rivera said his 11-day visit left him convinced that the Sandinista leadership, although perhaps only to gain tactical advantages in the war and to improve its tarnished image, has decided to listen to Indian demands for land rights and increased autonomy. Since Indian goals are different from the Democratic Force's U.S.-backed ideological goals, he added, it is possible to seek separate agreements that would allow Indians to return to their lands in the Atlantic region.

Rivera's guerrilla forces were part of the Costa Rica-based Revolutionary Democratic Alliance until it split last June over refusal by Rivera and the independent-minded military leader Eden Pastora to join with the Nicaraguan Democratic Force as urged by the CIA. Fagoth's forces have been allied with the Democratic Force since the insurgency began on a large scale two years ago in Honduras with CIA funds and advice.

Left without a financial base since indirect CIA funding for the Revolutionary Democratic Alliance ended last summer, Rivera traveled to Honduras in September to launch his peace-making effort. Fagoth, although reluctant, was encouraged by sympathetic Honduran military officers, Rivera said, and key tribal leaders among Indian refugees in Honduras also offered support.

Referring to his interest in peace talks with Nicaragua's leaders, Rivera said: "We are not surrendering to the Sandinistas . . . . What we are doing is trying to take practical steps to reduce the suffering of our people. Why can't we make a political maneuver? Why the others but not us?"

Rivera said he sought advice from the U.S. Embassy in San Jose, Costa Rica, before his trip to Nicaragua and was counseled not to go. The embassy refused to comment on any advice to Rivera, saying such contacts are private.

Rivera said he also was discouraged from seeking a separate Indian accommodation with the Sandinistas during a subsequent meeting in Washington with Deputy Assistant Secretary of State L. Craig Johnstone.

But the office of Sen. Edward M. Kennedy (D-Mass.) acted as intermediary last month in initial contacts with Sandinista leaders and, along with French diplomats, helped arrange a second trip to Honduras last week for a meeting with Fagoth and the Indian council of elders, Rivera said.

On his arrival in Honduras Friday, however, Rivera was detained and held overnight along with a dozen Indian leaders who had preceded him to the Honduran capital. After repeated protests, the group refused to eat until provided with an explanation from Honduran officers. Instead, Saturday afternoon they were driven to the airport and loaded aboard a Costa Rica-bound airliner by forklift through a back door, he added.

Johnstone said in Washington, "I didn't discourage him from anything." He added, "We have had no communications with Honduras regarding his comings and goings."

A high-ranking State Department official said Rivera "doesn't speak for the Miskitos; he only speaks for some of them." He added that Rivera is "not a major factor" in the anti-Sandinista insurgency.

[Kennedy wrote a letter to President Roberto Suazo Cordova of Honduras asking him to guarantee Rivera's safety for the meeting, a congressional source said in Washington. In an article Monday in The New York Times, Kennedy urged the Reagan administration to back Rivera's effort for humanitarian reasons.]

Rivera attributed the turnabout by Honduran officers to intervention by the CIA, the Democratic Force and Fagoth.

Fagoth has denied he helped arrange Rivera's expulsion. The Democratic Force has made no public comment on the matter.

[Reuter reported from Moscow that the official Soviet news agency Tass said President Reagan had no proof for his assertion that Nicaragua-bound Soviet ships were carrying arms. Tass said Reagan's remarks, made in an interview in The Washington Times Wednesday, were part of Washington's attempts to cover up its military presence in Central America.]