A United Nations envoy, James LeMoyne, is holding eleventh-hour talks over the weekend with the Colombian government and rebels who control an area twice the size of Wales, in an attempt to prevent a resumption of all-out war.
President Andres Pastrana has warned that unless the two sides can find common ground, the Marxist rebels of the Revolutionary Armed Forces of Colombia (Farc) must abandon a peace zone he granted them, jocularly known as "Farclandia", by tomorrow night. An earlier deadline was postponed at UN urging, but thousands of government troops are massed near the rebels' southern haven.
"We're ready for the war. We've been ready since the beginning of talks," said one army officer as his 80-member counter-insurgency unit rested in the shade 60 miles from the zone. "We're going to go from palm tree to palm tree, from corner to corner, and [the Farc] will be there somewhere. We're going to smoke them out."
In the three years since "Farclandia" was created and negotiations began, the only concession by the guerrillas has been an agreement to swap prisoners in poor health. Most Colombians feel the Farc have flagrantly abused the demilitarised zone, using it as a hideaway for kidnapped hostages and a corridor for arms and drug trafficking.
The peace process ran into trouble three months ago when the president tightened restrictions on travel to the enclave and increased surveillance flights. When the rebels insisted that the controls be lifted before considering any concessions, Mr Pastrana's peace commissioner walked away from the table.
Guerrilla fighters can still be seen rumbling through the peace zone in pick-up trucks with tinted windows and no licence plates. But they have abandoned checkpoints and camps near urban areas.
As a testament to the youth of Farc fighters, one rebel left behind a notebook with simple love poems, and a tracing of two puppies from the cartoon 101 Dalmatians. Human rights groups have long accused the Farc of recruiting fighters as young as 13.
While the rebels seemed relatively unconcerned at the possible resumption of fighting, civilians in "Farclandia" have reason to be afraid. In the sun-scorched cattle town of San Vicente, the de facto capital of Mr Pastrana's "peace laboratory", shops closed early and their owners went home as soon as the government issued its first ultimatum. Others bundled up their belongings and left town.
Residents fear that ultra-right paramilitary death squads will enter the rebel haven behind the military and launch a bloody retaliatory purge. Colombia's 8,000-strong United Self-Defence Forces (AUC) have massacred suspected rebel sympathisers, using chainsaws and machetes on entire families.
"The civilian population is stuck in the middle," said Dr Luis Fernando Rivas, the director of San Vicente's small hospital. In a meeting with an International Red Cross volunteer, Dr Rivas listed the medical supplies he needed most, and the top three were for treating emergencies. "We are in a war, and this won't change," he said.
Genaro Rodriguez, the president of community organisations in the town, said: "The government has the will to protect us, but it's a difficult task. If the talks collapse, the government will have to give everyone here a bodyguard".
Mr LeMoyne has warned that the future of Colombia is at stake. "In the next days, we'll know if Colombia is choosing peace or war," he said.Reuse content