Negotiators for Nicaragua's Sandinista government and the Contra rebels started a second day of meetings today in the capital in an effort to end the nation's 6-year-old war. After a brief round of talks Friday night, the first ever in Managua between the U.S.-supported rebels and Sandinista leaders, the two groups met this morning for more extensive discussions. The meeting started at 9 a.m. (11 a.m. EDT) and was expected to last for about 12 hours. Forty high-level Contra officials, some in Managua for the first time since 1979, came ``in search of what (they) tried to attain for many years ... democracy and liberty for the Nicaraguan people,'' Adolfo Calero, head of the rebels' Nicaraguan Resistance, told a news conference. Earlier, he told reporters at Sandino International Airport that the Contra leaders' presence in Managua ``is a triumph'' for their cause. But Defense Minister Humberto Ortega, the Sandinistas' main bargainer, said, ``The victory is when we reach a definitive cease-fire. It doesn't involve mounting a publicity show, but of complying'' with a preliminary peace plan signed March 23. The talks mark the first time since the war began that the Sandinistas have allowed rebel leaders to openly come to Managua. They are designed to move the two sides closer to halting the fighting that has claimed more than 26,000 lives since it began in November 1981, according to the government. Agreement on details of the truce was reached during talks that concluded Friday in the southern border post of Sapoa, 90 miles from Managua. The two sides in those talks issued a statement that said ``considerable progress'' had been made in narrowing their differences and that additional discussions would be held. The talks were called for in the preliminary peace plan. As part of that agreement, a 60-day cease-fire went into effect on April 1 to give both sides time to work out a lasting peace. But the two sides were unable to agree on important issues such as verification that the Contra fighters have moved into seven designated cease-fire zones, how the rebels would be resupplied, and if they should be allowed to keep their weapons. ``We will try to seek mechanisms in order to guarantee physical and moral security for our combatants,'' said Azucena Ferry, a member of the rebel directorate. Under the agreement, the Contras were supposed to have gathered in the zones by Friday, but there was no indication that occurred. The Sandinistas, in return, were to have released 700 political prisoners, allowed humanitarian aid for the rebels and permitted the insurgents to send representatives to take part in internal political discussions. The Contra leaders arrived more than four hours late on a commercial flight from San Jose, Costa Rica, and relatives gathered at the airport to greet them. Violetta Chamorro, the co-owner of the opposition newspaper La Prensa, waited to see her son, Contra leader Pedro Joaquin Chamorro, returning to Managua for the first time since 1986. Earlier, her newspaper's building was the target of a protest by about 300 teen-agers who pelted the building with rocks to protest the publication's pro-rebel stand. The demonstrators said they belonged to a group called Sandinista Youth. Witnesses who insisted on anonymity said a young man was slightly injured by a pail thrown from the roof. The Interior Ministry immediately banned all demonstrations and alcohol sales around the airport and hotel where the Contras were staying and closed the main road to the airport. Contra leaders claim they have about 10,000 rebels under arms. The Sandinistas claim they have an armed force of 300,000 men and women, including an 80,000-man army. The cease-fire was called for under a Central American peace plan signed by five Central American presidents last August.