The image is seared in Colombian minds: The country's president sits on a big stage looking glum, hands folded in his lap, next to an empty chair.

It is January 1999. At the inauguration of peace talks, the founding leader of the Western Hemisphere's biggest leftist rebel army has snubbed President Andres Pastrana.

Cursed, the peace talks drag on for three years in a safe haven the size of Switzerland that the government has ceded to the Revolutionary Armed Forces of Colombia, or FARC, which wages war elsewhere, kidnaps and extorts unabated and expands its cocaine business.

Ten years later, in a wealthier, far more stable Colombia, a different president is giving peace yet another chance.

"Any responsible leader knows he can't let pass up a possibility like this to end the conflict," President Juan Manuel Santos told the nation Tuesday in announcing an accord with the peasant-based FARC to seek "a definitive peace."

It will be the fourth such effort in three decades.

The pact, signed Aug. 27 after six months of secret exploratory talks in Cuba, calls for talks to begin in Norway the first half of October, then return to Havana.

"No doubt there are risks," said Santos, a 61-year-old economist and former journalist. "But I believe history would be much more severe with us all if we did not seize the opportunity."

After taking office in mid-2010, Santos said the FARC, badly weakened by a decade-long U.S.-fortified military buildup, would need to seriously curtail hostilities if its peace overtures were to be taken seriously.

Yet, at the same time, he was secretly cultivating rebel contacts.

And the peace talks will proceed without any halt in combat.

"It's going to be so much harder to negotiate while people are being extorted and oil pipelines are being attacked, child soldiers are being recruited and land mines are being laid," said Adam Isacson, a Colombia expert with the Washington Office on Latin America think tank.

The Andean nation's internal conflict, which has claimed tens of thousands of lives, has not persisted a half-century by accident. It is maddeningly complex in a country with one of the world's widest gaps between rich and poor and the second largest internally displaced population after Sudan.

Potential spoilers to a peace deal abound, particularly to the agrarian reform and rural development that Santos, a social progressive, says he will seek.

Resistance can be expected from wealthy rural ranchers and plantation owners allied with Alvaro Uribe, who as president from 2002-2010 waged war without quarter against the FARC while making peace with far-right militias known as paramilitaries who did most of the dirty war killing.

"How sad that FARC murderers and kidnappers are today political figures speaking to all the world with their deceptions," Uribe tweeted Tuesday after watching a videotaped speech by the rebels' leader, Timoleon Jimenez, broadcast from Havana on Tuesday.

And then there is drug trafficking.

It fuels all of Colombia's illegal armed groups: the paramilitaries, their successor gangs and the FARC itself.

"It is probably one of the most complicated (impediments to peace)," said Arlene Tickner, a political scientist at Bogota's University of the Andes.

That is because U.S. policy in Colombia has been almost completely governed by drug war politics.

Five of the six members of the FARC's ruling Secretariat, including Jimenez, are deemed major drug traffickers by the U.S. State Department, which has $5 million bounties out for each of them.

It is not clear how Washington would deal with them if the conflict ends. Colombia's congress passed a law in June that sets a framework for amnesties and pardons for rebel leaders.

Police and soldiers in Colombia mixed up in the illegal drug trade aren't exempt from prosecution. Would FARC commanders get a waiver?

Pastrana, who served as Colombia's ambassador to Washington after his presidency, called drug trafficking "a very important element" of peace talks and said "it would be good to invite the United States as well into this process."

Washington is a close ally of Colombia, but Santos has already exhibited considerably more independence than Uribe.

The White House issued a statement Tuesday praising the preliminary accord as a "milestone" and asking the FARC to "take this opportunity to end its decades of terrorism and narcotics trafficking."

The accord was brokered by Norway and Cuba and they will "facilitate" the talks while Venezuela and Chile "accompany" them. What that means is not yet clear.

Jimenez, better known as "Timochenko," acknowledged that a decade of intense military pressure, including the killings in raids of two top FARC leaders since Santos took office, had helped bring the rebels to the negotiating table.

It has lost roughly half its fighters in the past decade as Washington funneled an average of $700 million a year in mostly military aid to the government.

That has not prevented the FARC from stepping up hit-and-run attacks in recent months, targeting oil and coal installations in raids that have cost Santos politically.

But the insurgency has also suffered from increasingly more effective air attacks, thanks in part to sophisticated U.S. infrared and targeting systems fitted on its warplanes.

About three years ago, Colombia's military also began using Scan Eagle unmanned aerial vehicles bought from the United States, Gen. Douglas Fraser, the U.S. Southern Command chief, recently told The Associated Press.

Santos stressed Tuesday that he will not cede an inch of territory: "Military operations will continue with the same or stepped-up intensity."

He also said the talks would not be open-ended,

"They will be measured in months, not in years," he said. "If there are not advances, we simply won't continue."

Colombian society will have little patience, though, if tangible results are not soon forthcoming, many analysts believe.

"Santos is taking a huge political risk," said Michael Shifter, president of the Inter-American Dialogue think tank. "It is still far from clear whether the FARC is serious this time."

Shifter believes the issue will consume the second half of Santos' four-year term.

Santos has yet to announce whether he will seek re-election.