After a half-century of combat that spilled blood across this South American nation, Colombians have embarked on a new, but difficult path to settle their political differences with the signing of a historic peace accord between the government and leftist rebels.

The first test after Monday's signing is a weekend referendum in which voters are being asked to ratify or reject the deal. If it passes, as expected, Colombia will move on to the thornier and still uncertain task of reconciliation.

President Juan Manuel Santos and Rodrigo Londono, top commander of the Revolutionary Armed Forces of Colombia, formally signed the agreement before a crowd of 2,500 foreign dignitaries and special guests, including U.N. Secretary-General Ban Ki-moon and U.S. Secretary of State John Kerry.

Many in the audience, all dressed in white, had tears in their eyes as Santos removed from his lapel a pin shaped like a white dove that he has been wearing for years and handed it over to his former adversary, who fastened it to his own shirt.

It was one of many symbolic gestures during the 90-minute ceremony overlooking the colonial ramparts of Cartagena that filled Colombians with hope and optimism for the arduous work ahead implementing a 297-page accord that took four grueling years to negotiate.

If the accord is accepted by Colombian voters in Sunday's referendum, as polls say it will, the FARC's estimated 7,000 fighters would have to turn over their weapons gradually to a team of United Nations-sponsored observers within six months.

A much tougher challenge will be reconciliation, a process that will require rebels and state actors who want to avoid jail to confess their war crimes committed during a 52-year conflict marred by brutalities on both sides.

Longer term, the two sides have drafted an ambitious agenda to hasten the development of Colombia's long-neglected countryside and rid it of illegal coca crops that starting in the 1980s strengthened the FARC — and some say morally corrupted it — while other insurgencies across Latin America fell to the wayside.

Londono, best known by his alias Timochenko, called Santos "a courageous partner" and proclaimed there was no turning back on the FARC's decision to abandon Colombia's jungles.

"Let no one doubt that we are going into politics without weapons," he said before ending his speech with a simple but loudly applauded appeal for forgiveness

"I apologize for all the pain that we have caused," he said.

Santos, who for years was the FARC's top military opponent, was equally emphatic that he would honor his promise to promote pluralism and open up Colombia's traditionally elite-driven political system.

"As head of state of the fatherland we all love, I want to welcome you to democracy," he said. Earlier, he led the crowd in chants of "No more war! No more war! No more war!"

Across the country, Colombians celebrated with a host of activities, from peace concerts to a street party in the capital, Bogota, where the signing ceremony was broadcast live on a giant screen.

The signing was greeted with wild cheers followed by calls for Timochenko to be president from about 1,000 FARC rebels in the Yari Plains, a remote area of southern Colombia where the group recently concluded its last congress as a guerrilla army by endorsing the deal.

But there were also sporadic protests, including one in Cartagena led by conservative former President Alvaro Uribe, whose decade-long, U.S.-backed military offensive forced the FARC to the negotiating table. Shouting "Santos is a coward," the few hundred Uribe supporters vowed that if they gain power when the presidents steps down in 2018 they will undo an accord they say is harbinger of a Cuba-style leftist dictatorship.

The stiff domestic opposition, which will make implementation even tougher, contrasts with almost universal acclaim abroad for the accord. On Monday, European Union foreign policy coordinator Federica Mogherini said that with the signing of the peace agreement, the EU would suspend the FARC from its list of terrorist organizations.

The U.S. has yet to follow suit but Kerry said he is open to reconsidering its status.

"We clearly are ready to review and make judgments as the facts come in," he told reporters. "We don't want to leave people on the list if they don't belong."

Colombians' distrust of the FARC runs deep. Many families have been touched by rebel kidnappings and it will take years to heal the wounds from a conflict that claimed 220,000 lives and drove 8 million people from their homes.

The rebels are equally skeptical of the government on which they will now depend for protection, a fact underscored by Timochenko's startled look when a low flyover by three fighter jets unexpectedly interrupted his speech.

"This time they came to salute peace instead of unload bombs," he joked upon resuming.

Timochenko took over as the FARC's commander in 2011 after an aerial attack killed his predecessor shortly after he authorized a secret backchannel dialogue with the government.

For all of the challenges ahead, though, many Colombians who thought peace would never come were carried away with emotion.

"This is something I waited for my whole life — that I dreamed of every day," said Leon Valencia, a former guerrilla who is one of the most respected experts on Colombia's conflict. "It's like when you're waiting for a child that is finally born, or seeing an old lover or when your favorite team scores a goal."


Associated Press writers Vivian Salama and Pedro Mendoza in Cartagena, Cesar Garcia in Yari Plains and Libardo Cardona in Bogota contributed to this report.


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