President Daniel Ortega insisted today that Nicaragua can find peace only if the Reagan administration halts "terrorist aggression" by U.S.-backed insurgents and resumes direct negotiations with the Sandinista government.

Under these conditions, he said in a speech, the Nicaraguan government would be prepared to halt military operations against the rebels and allow them to return home under U.N. or Red Cross supervision so they could "make their lives in Nicaragua."

Once this occurred, he said, Nicaragua could return to "normalcy," an apparent allusion to lifting restrictions on liberty imposed as part of a three-year-old state of emergency.

Ortega's declarations appeared to be largely a repackaging of Sandinista demands for renewal of direct talks with the United States at Manzanillo, Mexico, which Washington suspended last January, and of the government's standing offer of amnesty for rebels who lay down their arms.

The speech, to a group of farm workers at Juigalpa in central Nicaragua, paralleled a memorandum given to Sens. John F. Kerry (D-Mass.) and Tom Harkin (D-Iowa) after a series of talks here last week with Sandinista officials, including Ortega. Broadcast over the official Voice of Nicaragua, the comments came two days before a scheduled congressional vote on renewal of U.S. funding for anti-Sandinista rebel forces fighting a guerrilla war here since 1981.

Congress halted CIA funding of the insurgents last spring after approving about $80 million over three years. It approved $14 million in renewed funding last fall, however, on condition the approval be endorsed in another vote this spring.

The vote, now set for Tuesday, has become a major test for President Reagan's attempts to pressure the revolutionary Sandinista government and prevent what he repeatedly has warned will be consolidation of a Marxist-Leninist system posing a security threat to Central America and, ultimately, the United States.

Recognizing the political stakes, the Sandinista government has sought to encourage a negative vote. Ortega said last week, for example, that he would feel a "moral" obligation to make some gesture if, as indicated by reports from Washington, Congress rejects the president's pleas for renewed funding. It was unclear whether today's declaration and the memorandum presented to Kerry and Harkin were designed as that gesture.

Observers noted the memorandum included more explicit pledges about restoration of civil liberties, such as freedom of the press, than the speech, which talked only of "normalcy." At the same time, they noted, the Sandinista government routinely has portrayed the restrictions as a necessity imposed by the war and said they could be lifted if fighting ceased.

In any case, Ortega's tone seemed tough and betrayed no fear that the funding measure would be approved by Congress. Although the speech dealt principally with economic issues, the Sandinista leader referred directly to Reagan's recent cease-fire proposal and conversations about it that he has held with a number of congressmen during the past two weeks.

"We said to the U.S. visitors that this situation we are facing is a situation that must be dealt with by way of dialogue, a peaceful solution," he told the assembled farmers. "Dialogue with whom? A dialogue with he who directs the aggression . . . . You have to talk with the government of the United States."

As the government has in the past, Ortega said the insurgents are "dogs" and only by talking to their masters could any solution be reached. "You have to talk to the one who sics the dog on you," he added.

Ortega reiterated that any cease-fire would have to be initiated by the Reagan administration and its allies in the insurgency.

The main rebel group, the Honduras-based Nicaraguan Democratic Force, on several occasions has proposed a cease-fire, accompanied by dialogue between the government and the rebels. This was the proposal picked up by Reagan to encourage approval by Congress. But the Sandinistas have held firm to their demands for dialogue directly with the United States, depicting the insurgents as a creation of the CIA.

"They the United States are the ones firing on Nicaragua," Ortega said. "So if they ceased fire, if they decided to resume the Manzanillo conversation, to normalize relations . . . in these conditions, we can then tell the mercenaries, 'Gentlemen, we are going to stop firing and halt military operations against you so that, through the Office of the U.N. High Commissioner for Refugees and the Red Cross, then you can put down your arms and you can make your lives here in Nicaragua.'

"Those who want to stay in Honduras, let them stay in Honduras," he added. "Those who want to stay in Costa Rica, let them stay in Costa Rica."

The Democratic Force, with approximately 12,000 armed men, has rear camps in Honduras. The other, smaller guerrilla force, headed by former Sandinista commander Eden Pastora, has its camps along the border with Costa Rica.