CARTAGENA, Colombia (AP) — Colombia takes a big step Monday toward emerging from its decades-long nightmare of bloody violence when the government and the country's largest rebel movement sign a peace accord that emerged from four years of negotiations.

The significance of the deal can't be overstated: Colombia's five-decade conflict, partly fueled by the nation's cocaine trade, has killed more than 220,000 people and driven 8 million from their homes.

Underlining the importance of the day, Colombian President Juan Manuel Santos and the top commander of the Revolutionary Armed Forces of Colombia, of FARC, a rebel fighter known by the alias Timochenko, will sign the accord in the colonial city of Cartagena. Fifteen Latin American presidents as well as U.N. Secretary-General Ban Ki-moon and U.S. Secretary of State John Kerry are to witness the signing.

In a ceremony charged with symbolism, the more than 2,500 guests have been asked to wear white as a sign of peace and Santos will sign the 297-page accord with a pen made from a recycled shell used in combat.

The signing won't close the deal, however. Colombians are being given the final say on endorsing or rejecting the accord in an Oct. 2 referendum. Opinion polls point to an almost-certain victory for the "yes" vote, but some analysts warn that a closer-than-expected finish or low voter turnout could bode poorly for the many challenges the country faces in implementing the ambitious accord.

Among the biggest and most controversial steps will be judging the war crimes of guerrillas as well as state actors. Under terms of the accord, rebels who lay down their weapons and confess their abuses will be spared jail time and will be allowed to provide reparations to their victims by carrying out development work in areas hard hit by the conflict.

A few hundred opponents of the deal took to the streets Monday to protest what they consider the government's excessive leniency toward guerrilla leaders responsible for scores of atrocities.

To shouts of "Santos is a traitor," conservative former President Alvaro Uribe, the architect of the decade-long, U.S.-backed military offensive that forced the FARC to the negotiating table, said that the peace deal puts Colombia on the path to becoming a leftist dictatorship in the mold of Cuba or Venezuela.

"The democratic world would never allow bin Laden or those belonging to ISIS to become president, so why does Colombia have to allow the election of the terrorists who've kidnapped 11,700 children or raped 6,800 women?" he told protesters gathered in a working-class neighborhood on the outskirts of Cartagena.

The government has also committed itself to addressing unequal land distribution, which has been a longstanding FARC demand harkening back to its roots as a peasant army in 1964, and the administration agreed to work with the guerrillas to provide alternative development to tens of thousands of families that depend on the cocaine trade.

Only if the accord passes the referendum will the FARC's roughly 7,000 fighters begin moving to 28 designated zones where over the next six months they are to turn over their weapons to U.N.-sponsored observers.

Negotiations, which had been expected to take a few months, stretched over more than four years and had to overcome a number of crises, from the military's killing of the FARC's then top commander, known as Alfonso Cano, shortly after he authorized a secret back channel with the government to the rebels' capture of an army general who until a few months ago would have been a trophy prisoner.

"What's good about the fact that it lasted four years is that it was a very thorough process," Norwegian Foreign Minister Borge Brende told The Associated Press in an interview ahead of the ceremony. Norway and Cuba were co-sponsors of the negotiation that began in Oslo in 2012 and then shifted to Havana.

"The mindset of everyone has changed," Brende said. "I feel very genuinely that President Santos and Commander Timochenko want this to work and not go into the blame game."

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Joshua Goodman is on Twitter: https://twitter.com/apjoshgoodman . His work can be found at http://bigstory.ap.org/journalist/joshua-goodman .