After sealing a historic peace accord with the FARC rebels, the Colombian government launched a campaign Thursday to persuade voters to adopt it in a referendum on October 2.
After four years of arduous negotiations in Cuba, the effort to end the civil war -- which has killed hundreds of thousands of people across more than half a century of fighting -- now comes down to a yes-or-no vote.
President Juan Manuel Santos, who has staked his legacy on the peace process, faces a tough political battle to win the referendum.
His top rival, former president Alvaro Uribe, is leading a campaign to vote "No" to the deal, arguing that his successor has given away too much to the Marxist guerrillas of FARC, or the Revolutionary Armed Forces of Colombia.
Uribe told the newspaper El Heraldo he would give a speech on the deal Friday, once he has been able to read the final text -- which Santos was due to send to Congress on Thursday.
Santos wasted no time in launching the "Yes" campaign.
Speaking on national television Wednesday just after peace negotiators in Havana announced the deal, he told voters the referendum would be the most important election of their lives.
"This is a historic and unique opportunity... to leave behind this conflict and dedicate our efforts to building a more secure, safe, equitable, educated country, for all of us, for our children and grandchildren," he said.
Opinion polls are mixed on how Colombians will vote.
The accord will take effect only if the "Yes" camp wins a majority while gathering at least 4.4 million votes -- 13 percent of the electorate.
Other obstacles to peace remain.
The government is still fighting a smaller rebel group, the National Liberation Army (ELN), whose ongoing kidnappings have derailed efforts to open peace negotiations.
And it will have to come up with the money to finance rural infrastructure projects and other carrots offered to the FARC, at a time of economic slowdown.
US President Barack Obama, who called Santos on Thursday to congratulate him on the "historic" news, acknowledged the tough road ahead.
"Even as we mark the end of an era of war, we recognize that the work of achieving a just and lasting peace is only beginning," he said.
UN Secretary General Ban Ki-moon and EU foreign affairs chief Federica Mogherini also hailed the deal but warned of the challenges ahead.
Obama vowed continuing support for Colombia, a key ally in the US war on drugs.
Washington has spent more than $10 billion on a joint anti-narcotics strategy called "Plan Colombia" -- recently rebooted as "Peace Colombia" by Obama.
Colombians welcomed Wednesday's announcement with both skepticism and joy. Many took to the streets, waving the national flag and carrying balloons emblazoned with the word "Yes."
The conflict began with the founding of FARC in 1964, at a time when leftist guerrilla armies were fighting to sow revolution throughout Latin America.
Over the years, the conflict has killed an estimated 260,000 people, uprooted 6.8 million and left 45,000 missing.
Along the way, the fighting has drawn in several leftist rebel groups and right-wing paramilitaries. Drug cartels have also fueled the violence in the world's largest cocaine-producing country.
Now, 25 years after the Cold War, Colombia's civil war is the last major armed conflict in the Americas.
The peace accord comprises six separate deals, covering justice for victims of the conflict, land reform, political participation for ex-rebels, disarmament, a fight against drug trafficking, and the implementation and monitoring of the accord.
Under the deal, the FARC will begin moving its estimated 7,000 fighters from their jungle and mountain hideouts into disarmament camps set up by the United Nations, which is helping monitor the ceasefire.
The FARC will then become a political party.
Special courts will be created to judge crimes committed during the conflict.
An amnesty will be granted for less serious offenses. But it will not cover the worst atrocities, such as massacres, torture and rape.
Those responsible for such crimes will face up to 20 years in prison, with lighter sentences if they confess.