Following the latest display of discord in Central America, the Contadora nations today resumed their efforts to promote a peace and security treaty acceptable to the region's five nations and the United States.

The persistence of negotiations, despite daunting odds and a three-year record of unfulfilled hopes, reflects a conviction by the Contadora governments and some of their Central American counterparts that keeping the talks going -- even fruitlessly -- represents the best way to prevent broader and bloodier conflict in the area.

More immediately, according to several officials closely involved in the effort, the negotiations provide an acceptable alternative for U.S. congressmen seeking ways to oppose the Reagan administration's proposal for $100 million in mostly military aid for anti-Sandinista rebels attacking Nicaragua.

This was a key factor in a decision by the five Central American presidents at a summit conference Sunday to drop mention of a June 6 deadline for signature of the proposed Contadora treaty, according to one of the presidents. Leaving the talks open-ended, he explained, means they can survive as a debating point in Washington even if little progress is made before the deadline, which was imposed by the Contadora governments at a round of talks last month in Panama.

The aid measure, which was approved by the Senate last month but rejected by the House, has been scheduled for reconsideration next month. These Latin officials hope, however, that the vote might be delayed as long as the Contadora negotiations show even a remote promise of success.

President Daniel Ortega of Nicaragua announced yesterday that the Sandinista leadership is offering new proposals on arms limitations, providing grist for further negotiations on an issue that previously had produced an impasse.

Deputy foreign ministers of the Contadora countries -- Mexico, Colombia, Venezuela and Panama -- resumed in Panama today the negotiations they had suspended over the weekend while the five Central American presidents met in Esquipulas, Guatemala.

The question of arms limits and controls is one of the main points that have prevented conclusion of a treaty since the effort began in January 1983 on Contadora Island off Panama. Softening an earlier Sandinista stand, Ortega told a news conference in Managua that Nicaragua now is willing to discuss limits on offensive arms -- he listed planes, rockets, tanks and artillery as examples -- but not defensive arms, such as the AK47 automatic rifles distributed to the Popular Sandinista Militias.

Previous Sandinista positions had maintained the Nicaraguan military could not afford to reduce its armaments to a level equal to that of other Central American countries because Nicaragua alone faces a threat from the United States. Ortega said the new position was forwarded to the four other Central American presidents in Esquipulas.

At the same time, he reiterated that Nicaragua insists on an end to, not merely regulation of, foreign participation in Central American military maneuvers.

The United States has held a series of large-scale military maneuvers with Honduras over the last four years, some of which have had the effect of helping the anti-Sandinista rebels by preparing airfields later used by the guerrillas. Nicaragua has charged the maneuvers also have been designed to prepare Honduras as a trampoline for a possible U.S. attack on Managua.

In a measure of the divisions in Central America, the Honduran government, a key U.S. ally, immediately denounced Ortega's announcement as a public relations gimmick. A government spokesman in Tegucigalpa told news agencies: "Honduras has the political will to reach a definitive [Contadora] agreement and not to enter into a Byzantine discussion on which arms are defensive and which are offensive, because this would be like asking how many angels fit on the head of a pin."

But one of the presidents in Esquipulas, who requested anonymity, said the Nicaraguan proposals, while unacceptable as they stood, marked the basis for further negotiations and would be considered at subsequent Contadora negotiating sessions such as the one beginning today.

Attention has faded in recent weeks from another major obstacle to the Contadora treaty. This is the insistence by Nicaragua that any accord be accompanied by cessation of U.S. support for the anti-Sandinista rebels, often called contras from the Spanish word for counterrevolutionaries.

While that argument has been set aside in favor of arms controls discussions, it has not gone away. Ortega reiterated that, in his judgment, even a negative congressional vote cannot prevent President Reagan from keeping the rebel forces fighting. "The contras will remain as long as the United States desires it," he said.

Another obstacle appeared to gain in importance during the Esquipulas meeting. This was the insistence by President Oscar Arias of Costa Rica that any Contadora accord contain verifiable procedures to guarantee democratic government in Nicaragua.

Arias said in an interview that most Central American violence has grown from lack of democracy, making authentic democracy a prerequisite for lasting peace.

With the Costa Rican idea of authentic democracy differing greatly from the Sandinista idea, this position appeared likely to become another major sticking point.