Colombian President Juan Manuel Santos won the Nobel Peace Prize for his efforts to end a 52-year-old war with Marxist rebels, a surprise choice and a show of support after Colombians rejected a peace accord last Sunday. (Reuters)

Five days after the worst defeat of his political career, Colombian President Juan Manuel Santos was awarded the Nobel Peace Prize on Friday for his dogged, but unfulfilled, effort to end a half-century of civil war.

The Norwegian Nobel Committee said it made the decision because of Santos’s landmark attempt to stamp out one of the world’s longest-running conflicts, which has killed more than 220,000 people and driven at least 7 million from their homes since 1964.

The award was a surprise because Colombians voted Sunday against Santos’s peace accord, which many viewed as too generous to the Revolutionary Armed Forces of Colombia (FARC). Santos was considered a leading candidate for the prize prior to the referendum, but his chances seemed to fade after voters sunk the deal by a narrow margin.

Offering a window into Nobel deliberations, the committee said its members were conscious that the Colombian peace efforts were imperiled and wanted to offer a boost.

“There is a real danger that the peace process will come to a halt and that civil war will flare up again,” said Kaci Kullmann Five, a former Norwegian politician who is now chair of the Norwegian Nobel Committee. “We hope it will encourage all good initiatives and all the parties who could make a difference in this process in Colombia.”

Santos’s award was celebrated in Colombia, whose only previous Nobel winner was the late novelist Gabriel García Márquez , recipient of the 1982 prize in literature.

Santos dedicated the prize to the Colombian people and the millions who have suffered from the bloodshed.

“This is for the victims,” he said in a nationally televised address Friday morning. “So that there won’t be one more victim, nor one more death. We must come together and unite to complete this process, and begin to build a stable and lasting peace.”

Among the surprises of the award was that it was bestowed on Santos alone, rather than the president and his main partner in the peace efforts, FARC leader Rodrigo Londoño, who goes by the alias Timochenko.

But the FARC leader was never considered as strong a candidate for the honor. Like other guerrilla commanders, he is wanted in the United States on drug-trafficking charges, and he leads a rebel army that the U.S. and Colombian governments consider a terrorist organization.

Londoño said Friday on Twitter that he remained committed to peace, and the rebels issued a separate joint statement with government negotiators saying the FARC would be willing to discuss “adjustments” to the accord.

Colombian President Juan Manuel Santos, with his wife, Maria Clemencia Rodriguez, reacts after casting his vote on the peace accord referendum Sunday. (Mario Tama/Getty Images)

It appeared to be the first time the rebels have indicated a willingness to revisit the 297-page agreement, which was formally signed by Londoño and Santos on Sept. 26 but can’t be implemented because voters rebuffed it.

Norway had a special stake in this year’s peace prize. Its government, together with Cuba, has served as a “guarantor” for the negotiations with the FARC, essentially playing a mediator role throughout four years of painstaking talks.

Whether the Nobel prize will give Santos new leverage to rework the peace deal remains to be seen.

Colombians already knew that Santos had the support of the Obama administration, the United Nations, the European Union and Pope Francis — an immensely popular figure in their heavily Catholic nation of 50 million . The pursuit of a peace deal with the guerrillas “was a deeply personal conviction for him,” said Pilar Calderon, who worked closely with Santos as his communications director for two years, until April.

But it appeared to make little difference in Colombia, where Santos’s popularity is significantly lower than it is abroad. With the economy slowing and crime on the rise, Santos’s presidential approval rating has slumped below 30 percent in recent months. His opponents were able to defeat his peace deal Sunday in part by making the vote a referendum on his presidency.

Calderon said she expected that some in the deeply polarized country will say that Santos’s long campaign for a pact with the rebels was motivated by personal “vanity” and a kind of prize-chasing.

“They’re wrong,” she said. “He did it because he knows that the only way for Colombia to move forward is with peace.”

The Harvard-educated scion of one of Colombia’s most prominent families, Santos, 65, was the nation’s defense minister from 2006 until 2009, a period when the Colombian military dealt the FARC some of its toughest setbacks.

In a region long polarized by ideology, he is viewed as a new kind of statesman, a pro-business, socially liberal, globally minded centrist on a laudable quest to end his country’s bloody, bitter war.

The future of the efforts is in flux. Ordinary FARC soldiers have already spent months preparing to lay down their arms and rejoin their families. Any new deal will probably include harsher penalties for those accused of kidnapping, drug trafficking, murder and other war crimes. Many rebels have spent decades in the jungle.

Absent any breakthroughs, a fragile cease-fire will expire Oct. 31.

Santos faced a major challenge from his former political benefactor and predecessor as Colombia’s leader, Álvaro Uribe, who led the successful effort to derail the peace accord.

“I congratulate President Santos for the Nobel,” Uribe wrote on Twitter on Friday morning. “I hope it leads to changes to the accords that are damaging for democracy.”

If Uribe pushes for a deal that the rebels can’t accept, the peace accord could crumble. If he and the guerrillas can reach a compromise, he, more than Santos, could play the peacemaker role.

But the Nobel prize “moves the dial back toward Santos,” said a source involved in the negotiations, who spoke on the condition of anonymity because of the delicate state of the talks. “This solidifies international support and puts extra weight on Uribe to not be the guy who kills the peace. Whether it’s enough, or whether Uribe will see it that way, is another story.”

Santos and Uribe met at the presidential palace for the first time in six years Wednesday, but they have yet to agree on a path forward or which elements of the peace deal could be rewritten.

Michael Shifter, president of Inter-American Dialogue, a Washington think tank, said there is a risk that the prize could make it even harder to put the process back on track, “given that the bad blood between Uribe and Santos stems from envy as much as anything else.”

“Hopefully both will be magnanimous and work together to forge a national consensus on peace,” Shifter said. “It would be a pity if this ended up being the ultimate consolation prize for Santos.”

Miroff reported from Havana. Annabell Van den Berghe in Brussels contributed to this report.