MANAGUA, NICARAGUA, JUNE 15 -- President Violeta Chamorro today announced cuts that would reduce the Nicaraguan armed forces by one-third, leaving them slightly more than half the size they were when she took office, and promised that by the end of the year, service in the army would be completely voluntary.

Chamorro's announcement came as the last 1,000 contra rebels began turning in their weapons to United Nations peacekeeping forces. The Nicaraguan president said 14,200 guerrillas have been disarmed so far.

"We can now say with absolute certainty that we have left the war behind," the Nicaraguan president said in a brief speech before members of her government and foreign diplomats. "Instead of burying children in a war between brothers, may we bury forever our weapons," she said, vowing to work toward the abolition of armies throughout Central America.

Under the reduction plan, the Nicaraguan army will be cut from about 61,000 soldiers to 41,000 by the end of July. When Chamorro took office on April 25, the Sandinista Popular Army plus militia and reserve forces were estimated to number about 80,000. Almost 20,000, mostly draftees, left the armed forces immediately following Chamorro's inauguration.

At the height of Nicaragua's war against U.S.-supported contras, the Sandinista forces were estimated at more than 110,000 troops.

Alberto Lacayo, Chamorro's son-in-law and closest adviser, told reporters tonight in Guatemala City that the latest cut would come entirely from among draftees, militia and reservists and indicated that it was only the first step of drastic reductions to be continued after August.

Chamorro said the army's remaining conscripts would be released from service by Dec. 7. Abolition of the highly unpopular military draft was one of Chamorro's main campaign promises.

Chamorro announced the cuts a few hours before departing for a regional summit conference in Guatemala, which is expected to focus on economic issues rather than the civil wars in Nicaragua and El Salvador that have dominated previous meetings. She said she would raise the issue of multilateral military cuts with the presidents of Costa Rica, Guatemala, El Salvador and Honduras.

The army already has begun collecting weapons from Sandinista civilians and rural militia. Government sources, however, say that so far fewer than 10,000 weapons have been turned in.

After the cuts, the army will be approximately the same size as the armed forces in El Salvador and Guatemala. But the Nicaraguan army will still be twice the size of the 19,000-member armed forces in neighboring Honduras. Costa Rica, Nicaragua's southern neighbor, abolished its army 40 years ago.

Chamorro has said repeatedly that the countries of Central America should follow Costa Rica's example, replacing expensive armies with lightly armed police forces. But in her speech she stopped short of promising the unilateral abolition of Nicaragua's army, talking instead of maintaining a "reasonable balance of forces in Central America."

Government supporters hope that reducing the army, which consumes about 40 percent of the budget, will free funds for investment in education, health care and the country's dilapidated infrastructure. They also hope the cuts will reduce the power of the army, still seen as the bastion of Sandinista party militants.

But while welcoming the cuts, members of Chamorro's own coalition criticized the government for allowing Gen. Humberto Ortega, the brother of ex-president Daniel Ortega, to remain as head of the armed forces.

At her inauguration April 25, Chamorro said Ortega would stay at his post temporarily to oversee the demobilization of rebel forces and the reduction of the military. But her government has not said how long it expects that process to take, and in her speech today, Chamorro made no mention of Ortega's tenure.

Ortega "casts a shadow over this government," said Ivan Madriz, a legislator in the governing coalition. "The Nicaraguan people will not feel safe until he leaves the army."Correspondent Lee Hockstader contributed to this story from Guatemala City.