MANAGUA, NICARAGUA, FEB. 5 -- President Daniel Ortega's stern call for a sustained Sandinista political and military offensive after the House of Representatives vote against aid for the Nicaraguan rebels may have sounded dissonant in Washington, but it was in tune with the concerns of Sandinista supporters in Nicaragua.

After six months of playing mainly to an international audience and within hours of the vote Wednesday night, Ortega consulted the other eight top leaders of Nicaragua's ruling party and abruptly turned his attention to its followers. Many are restless after a string of government concessions under a regional peace accord signed Aug. 7.

Ortega's message was designed to refuel their fervor in preparation for a period when, despite the congressional vote, Sandinista leaders expect intensified fighting with the rebels, known as contras, deepening economic crisis and sharper confrontation with opposition political parties.

"The vote doesn't change the situation, which remains critical . . . . We can't let down our guard," Ortega warned in a speech yesterday.

A question during the press conference that followed Ortega's address from Mario Zelaya, reporter for the progovernment Voice of Nicaragua radio, echoed Sandinista resentment: "You say the situation is difficult. Well, then, why does the government continue to be so generous? Why does Nicaragua have to give so much when other Central American countries are still being used in the war against us?"

In his speech Ortega accused El Salvador and Honduras of harboring contra military operations.

Sandinista predictions of bloodier warfare were confirmed within hours after Ortega's midday appearance when contras ambushed a truck carrying civilian passengers, killing 16 and wounding 16.

During the tense weeks before the House vote, reports circulated in Managua of a power struggle between Ortega and other, more radical members of the nine-man Sandinista National Directorate. In fact, the House vote was a major vindication for a survival strategy for the Sandinistas' eight-year-old revolution reportedly favored by Daniel Ortega and his brother, Defense Minister Gen. Humberto Ortega within the National Directorate.

The Ortegas, with the sometimes troubled approval of the other Sandinista comandantes, have moved on two tracks. The president exercises diplomacy, trying to control any U.S. military threat through negotiation. His brother oversees a massive, Soviet-supported military buildup of both antiguerrilla and conventional forces to guarantee the government's defense in case diplomacy fails.

The concessions required by Daniel Ortega's initiatives, and the massive spending that Humberto Ortega needs to sustain 80,000 regular soldiers and tens of thousands of reservists, impinge on projects of other comandantes who would like the government to have tighter political control or carry out more socialist reforms.

One senior Sandinista official said recently that the more serious gap arose between the top comandantes and Sandinista party militants, estimated to number about 30,000, and tens of thousands of members of grass-roots organizations sponsored by the party.

Many of the revolutionary rank and file were indignant about Ortega's announcements Nov. 5 and at a Jan. 16 regional summit in San Jose, Costa Rica, that led to face-to-face cease-fire talks with the contras. A fundamental tenet of Sandinista ideology is that the contras are U.S.-paid mercenaries who cannot be legitimate counterparts in a political negotiation.

Sandinista women's organizations also have lobbied hard against freeing from jail an estimated 2,200 former members of the National Guard of the late dictator Anastasio Somoza. The peace accords signed Aug. 7 in Guatemala call for a broad amnesty for political prisoners.

What Ortega offered his disgruntled followers yesterday was a reassurance that Sandinista leaders have not been lulled into trusting their principal enemy, the United States.