The Contadora nations handed over to representatives of five Central American nations what they called the "last version" of their proposed regional peace treaty today, urging leaders to sign the pact swiftly and negotiate details of a verification system later.

The four Contadora countries -- Mexico, Panama, Colombia and Venezuela -- also pledged at the conclusion of a two-day meeting here to continue their three-year-old effort to promote a Central American peace treaty despite failure to reach agreement by a self-imposed deadline of June 6.

As a result, the Contadora-sponsored peace talks appeared likely to continue indefinitely among the five badly divided Central American nations -- Nicaragua, Honduras, Costa Rica, El Salvador and Guatemala -- barring an explosion of the region's guerrilla wars or a broader conflict involving the United States and Nicaragua.

Some officials involved in the negotiations have said keeping them going has become one of the main objectives, providing at least the promise of an alternative to more U.S. aid for anti-Sandinista rebels or an outright U.S. attack on Nicaragua to remove its Marxist-led Sandinista government. The U.S. Congress has set mid-June for reconsideration of a disputed administration proposal to give the rebels $100 million more in mostly military aid.

"It [the peace negotiation] could go on for one year, or two years," said Foreign Minister Francisco Quinones of Guatemala.

"No more deadlines," said Vice President Rodolfo Castillo Claramount of El Salvador, who also is foreign minister.

The action here -- issuing the third draft treaty since the talks began on Contadora Island off the coast of Panama in January 1983 -- was designed to remove a growing impression that the peace negotiations had reached a dead end, one key participant said. By proposing a new version of the treaty and setting no deadlines for agreement, the Contadora countries opened the horizon for more talks without the specter of failure by another particular date.

"That's the sum total of it," said Foreign Minister Miguel d'Escoto of Nicaragua.

The measure was given added weight by the presence here of foreign ministers from Peru, Brazil, Uruguay and Argentina, the so-called "support group" of South American countries endorsing the Contadora enterprise.

Despite the grave differences between his country and the U.S.-allied governments of El Salvador, Honduras and Costa Rica, d'Escoto predicted a treaty could be agreed on by the end of July "at the latest."

In the new proposal, the most significant shifts took place in the section dealing with arms limits and military maneuvers, the most hotly disputed issues. Although the fresh draft included no radical departures from previous proposals, it marked an attempt to distill suggestions from several Central American countries, including assigning relative weight to different kinds of arms, and to balance the concerns of Nicaragua against those of its U.S.-allied neighbors.

The main split between Nicaragua and its U.S.-backed neighbors concerns armament levels and military maneuvers with foreign participation. In addition, President Oscar Arias of Costa Rica emphasized at a May 25 meeting of Central American presidents in Esquipulas, Guatemala, the need for verifiable guarantees of authentic democracy in all five countries, a concern he aimed chiefly at Nicaragua.

Nicaragua, while offering to limit offensive weapons, has maintained the need to have a larger military establishment than its Central American neighbors. To back its claim, it has cited the attacks by U.S.-sponsored rebel forces and what the Sandinista leadership says is a threat of invasion by the United States.

Honduras, a chief U.S. ally, has balked at Contadora proposals for severe limits on foreign participation in military maneuvers. The United States has carried out large-scale maneuvers in Honduras for the last four years, sometimes with the effect of helping the rebel logistics effort. In addition, Nicaragua has charged that the U.S. exercises have prepared Honduras as a platform for U.S. invasion forces if Washington decides to intervene.

Hovering around these concerns, although not officially part of them, is the Reagan administration's insistence that any Central American peace treaty must carry simultaneous and verifiable commitments from all five Central American governments, particularly on the question of military controls and nonintervention.

The Contadora governments, in a letter accompanying the draft turned over to the five Central American foreign ministers, seemed to be seeking to overcome the sticking point of security guarantees.

"Once this question is resolved, we propose immediately going on to another phase of negotiation . . . principally to the status of the commission of verification and control," the letter said.

This appeared to contradict a concern evoked most strongly by El Salvador, another key U.S. ally, according to a participant in the meetings here. Castillo Claramount emphasized what he said was the need to work out details of control and verification as part of the treaty, the source said. This also has been a major concern of the Reagan administration.