The five Central American presidents today expressed determination to sign and abide by a regional peace treaty but recognized that serious regional discord still prevents its conclusion by any specific date.

The declaration, at the end of a two-day summit conference here, represented the lowest common denominator of agreement among the divided Central American leaders. By its frankness, it underlined the obstacles blocking efforts to work out a comprehensive and detailed peace treaty envisaged in the three-year-old Contadora peace negotiations.

President Vinicio Cerezo of Guatemala, who organized the gathering, had proposed a broad statement of peaceful coexistence, reiterating the five countries' commitment to sign a Contadora treaty by June 6 and endorsing his idea for a Central American parliament to foster regional unity and create momentum for improved relations.

But the same disputes that have long prevented conclusion of the Contadora accord itself arose during the talks here, held in a monastery on the site of a Black Christ statue traditionally venerated by Central Americans. As a result, the five presidents prolonged their negotiations and finally agreed on the declaration only after stripping the proposal of its contentious points, according to an official present at the talks.

"We came out with a document that is a little thin," acknowledged Foreign Minister Carlos Lopez Contreras of Honduras.

Lopez Contreras said the commitment to sign a Contadora treaty by June 6, as contained in the proposed document, was abandoned because the presidents were unwilling to commit the prestige of their high office to a date that Central American officials and commentators increasingly regard as illusory.

"It's very risky for the presidents to announce they are going to sign on June 6 and then, for some problem or other, they can't," he said.

Two presidents said this was tantamount to an acknowledgement that the June 6 deadline could not be met. One explained that this tactic was desirable because it left open the possibility of a later agreement, retaining the Contadora negotiations as a dissuasive factor against more U.S. military aid for the anti-Sandinista rebels.

Manuel Espinoza, spokesman for President Daniel Ortega of Nicaragua, said the disagreements stemmed from insistence by "some delegations" on changes in the draft declaration that he said was initialed May 4 at a vice presidents' preparatory meeting in Guatemala City. He did not elaborate.

President Oscar Arias of Costa Rica said he objected to a draft clause referring to the five leaders as presidents "freely elected by the majority wills of their respective countries." He said he could not affirm Ortega was freely elected, and this set off a long discussion on the quality of democracy in the five nations.

"We have our concept of democracy and the president of Costa Rica has his," Ortega said after the conference.

As in the case of the commitment to sign a Contadora treaty by June 6, the reference was dropped.

Contreras said broader disagreements, on arms control and U.S. military maneuvers in Honduras, also were left unresolved. In recognition of this, the closing communique said the presidents "recognize there are still aspects to resolve, among them military maneuvers, arms controls and verification of fulfillment of the agreement."

Cerezo, who as host read the final declaration, said the presidents agreed that their respective positions were "forthcoming and realistic" enough to permit eventual agreement on a peace treaty. In that light, the declaration expressed the presidents' "will" to reach agreement on the treaty, "assuming its complete fulfillment with the totality of the commitments and procedures contained in it."

The presidents also agreed to form a commission within 30 days to draw up, in a three-month period, an agreement for the proposed Central American parliament, which they said would be elected with universal suffrage.

The presidents affirmed that peace in Central America "can only be the result of an authentic, pluralistic and participatory democratic process." In what was seen as a compromise with Nicaragua's Sandinista system in mind, the declaration also said that each country should be free to choose its own economic, political and social model "as long as this is a product of a freely expressed will of its people."

El Salvador, Costa Rica and Honduras, the three closest U.S. allies, lined up against Nicaragua in the talks, with Guatemala seeking to play a more neutral role, a Salvadoran official said. This has been the basic regional split since the Sandinista revolution in 1979. The same fundamental divisions have prevented a Contadora treaty since the peace-making effort was launched by Mexico, Colombia, Panama and Venezuela at a January 1983 meeting on Contadora Island off Panama.

As diplomatic pressure has mounted, Nicaraguan officials have charged that Arias and presidents Jose Napoleon Duarte of El Salvador and Jose Azcona of Honduras are taking their lead from Washington. The Sandinista government has long argued that the Reagan administration was seeking to prevent conclusion of a Contadora treaty because its real goal was to get rid of the Sandinista leadership.

The U.S. administration reiterated Friday that it would be prepared to respect the Contadora treaty if it were carried out and verified. This would imply ending U.S. sponsorship of anti-Sandinista rebels.

A major obstacle in Contadora negotiations has been Nicaraguan insistence that the Sandinista government can sign a treaty only if the United States also formally commits itself to stop supporting the rebel forces and vows not to attack Nicaragua. In the same vein, Nicaragua has said it cannot forswear a high level of armament, contending that it faces a threat from the United States and Central American states.

These have been the principal blocks to progress for more than a year in the Contadora negotiations.

Last night, El Salvador and Honduras agreed to refer to the World Court a border dispute pending since their brief "Soccer War" in 1969.