Colombia's military accused leftist rebels of killing 12 soldiers on Saturday as government and rebel negotiators met to advance fragile peace talks ahead of an approaching deadline.

The daylong talks in Los Pozos in a vast rebel safe haven in southern Colombia ended late Saturday without an announcement on an agreement. Negotiators said they would resume discussions Sunday morning.

President Andres Pastrana has said that if negotiators fail to agree on a timeline for cease-fire talks to end the country's 38-year civil war by midnight Sunday, then he will revoke the rebels' control of Switzerland-sized safe haven given them three years ago as a condition for talks.

"We have achieved some advances, but a lot of work remains," government negotiator Camilo Gomez told reporters.

On Saturday, Revolutionary Armed Forces of Colombia, or FARC, rebels blew up an army vehicle near Cali, Colombia's third-largest city, killing four soldiers who were trying to rescue rebel hostages, army Gen. Francisco Rene Pedraza said. Hours later, eight soldiers were killed nearby trying to fend off a rebel offensive, he said.

In other violence blamed on the FARC, its fighters on Friday forced down a helicopter on a drug-destroying mission in southern Caqueta province and killed five anti-narcotics officers, police said.

Rebels opened fire on the helicopter, forcing its crew to make an emergency landing, Col. Carlos Rivera of the anti-narcotics police said Saturday. About 200 guerrillas attacked 16 police officers who had stayed by the aircraft to protect it, killing five and wounding four.

Police also blamed the FARC for the slayings of a priest and his two cousins in Caldas province, saying rebels shot the three in the head at a roadblock Friday on a rural highway 80 miles northwest of Bogota.

Authorities say the rebels killed at least 40 people in attacks in the past week, but did not detail the other deaths.

The bloodshed has cast doubt over efforts to revive the fragile peace effort.

Meanwhile, diplomats from 10 countries and representatives from the Vatican and the United Nations were in Los Pozos, a town inside the safe haven, to try to nudge the sides toward progress.

Residents in the zone, which Pastrana ceded to the rebels in 1998 to jump-start peace talks, fear they will be caught in the crossfire if negotiations fail and government forces move in.

"We are going through psychological torture," said Luis Carlos Rincon, a store owner in San Vicente Del Caguan, the main town inside the rebel zone.

Colombia's civil war kills roughly 3,500 people every year, and involves government forces, an outlaw right-wing militia, the FARC and a smaller rebel army.

The United States is backing Colombia's drug war with millions of dollars in military aid to government forces. The FARC and right-wing militia both make money off drug production.