MANAGUA, NICARAGUA, OCT. 29 -- Nicaragua will neither lift its five-year-old state of emergency nor implement a broad political amnesty under a Central American peace accord until the United States ends all aid to the U.S.-backed rebels, the ruling Sandinista party announced tonight.

The statement, issued by the Sandinista National Liberation Front (FSLN) after a day-long assembly of its most important members, significantly hardened Nicaragua's position in the peace process as a Nov. 5 deadline for compliance with the pact approaches.

The government "no way, nowhere, through no intermediary, at no time will ever hold a political dialogue" with the highest leaders of the rebels, known as contras, the statement also said.

The Sandinista party's position paper was read in an hour-long speech at the assembly's close by the Sandinistas' top ideologue, Bayardo Arce, who is also one of nine top Sandinista commanders. The FSLN and its nine-man leadership wield the real power in Nicaragua.

The Sandinista dictum was the culmination of two weeks of tense debate within party ranks over how flexible the government should be with the peace plan, signed Aug. 7 in Guatemala by the five Central American presidents.

"We can't give an amnesty while the mercenary forces continue to assassinate our brothers. We can't suspend the state of emergency while peasants, old people, women and children are fired upon indiscriminately, while the organized aggression of the United States, which is precisely what gave rise in the first place to the emergency, persists," Arce read. The Sandinistas often refer to the contras as mercenaries.

The Reagan administration has said it will seek $270 million in new military aid for the contras but in recent days has indicated that it would delay a new funding request until after a January regional summit, when the five presidents are to assess the progress of the plan.

The statement said Nicaragua will move forward with new measures when the contra aid is stopped "with no subterfuge or delaying maneuvers." The peace pact calls on signatories to demand that outside powers halt aid to insurgent forces.

Washington has indicated that it would continue humanitarian aid to the contras. It is not a signatory to the pact but has supported it in general terms and could be expected to accede to demands regarding aid made by Honduras, through which aid to the contras has passed.

During a two-day Central American foreign ministers' meeting in Costa Rica that ended yesterday, Nicaraguan diplomats had said the government was preparing a broad amnesty to free as many as 75 percent of an estimated 4,500 political prisoners. Today's Sandinista statement seemed to put that measure on hold.

The ruling party said Nicaragua will insist that the accords be met as they are written. The text of the sweeping agreement does not require governments to hold talks with armed rebels, but only with political opposition groups. It is not specific about who should benefit from the mandated political amnesty.

The pact does say governments must lift any state of emergency to move toward a freer democratic environment. It also demands that all main clauses, including an end to foreign aid to guerrilla armies in the region, must go into effect at the same time in all five countries.

However, shifting pressures and events since Aug. 7 have moved the pact in new directions. Nicaragua has been pressed to hold talks with the contras to reach a cease-fire, because El Salvador and Guatemala initiated a dialogue with rebel organizations in those countries.

Nicaragua "will defend its right not to accept any demand which is not in the text of the accords," the Sandinista statement said. But it inisted that Nicaragua intends to comply "to the letter" with the agreement.

The government has initiated a dialogue with the opposition political parties, which is stalemated at this point. Arce added that the Sandinistas would not roll back any of their major revolutionary program because of the peace accord. "The Sandinista Front wants peace, but not the peace of cowards," he said.

Earlier today, in San Jose, Costa Rica, Nicaraguan Indian rebels said the Sandinista government had suspended scheduled peace talks with them, fearing that it might also be drawn into talks with top leaders of a larger rebel alliance.

A meeting between Sandinista officials and leaders of the Indian rebel army, named Yatama, was scheduled to take place last weekend. But hours before Indian representatives were to board a plane for Managua Saturday, Interior Minister Tomas Borge announced that they would not be allowed to return to Nicaragua without accepting a government amnesty.

The amnesty condition had been set aside by both sides during the previous week of intense negotiations, according to Yatama leader Brooklyn Rivera.

Costa Rican officials were optimistic last week that the cease-fire talks might take place, based on indications that President Oscar Arias had received from Nicaraguan President Daniel Ortega. But as wrangling inside the Sandinista party continued in Managua, Nicaraguan government officials returned to their earlier staunch rejection of a dialogue.