Colombian President Juan Manuel Santos, campaigning for a second term, is basing his bid on his confidence he will conclude a peace deal to end Latin America's oldest leftist insurgency.

Perhaps fittingly, the first round presidential vote, set for May 25, comes just two days before the 50th anniversary of the uprising by the Revolutionary Armed Forces of Colombia, or FARC.

The conflict is responsible for hundreds of thousands of deaths and displacing some five million people.

"We can't condemn further generations of Colombians to a never-ending and pointless war," Santos said in an exclusive interview with AFP.

But the president admitted that, even with a peace deal, the hardest work will still remain: preventing the former rebels from "transforming themselves into a new criminal structure," by creating an "efficient reintegration program."

According to authorities, the rebel group still has some 7,000 fighters.

The president warned "post conflict period could last up to 10 years."

Halfway through his first term, in late 2012, the center-right leader, who as defense minister inflicted on the FARC some of its worst military losses, announced the opening of peace talks with the rebel group.

Santos now professes himself "more optimistic" of success than at the beginning of the talks, the fourth attempt to negotiate peace with the FARC.

"A final agreement ending the conflict is possible before the end of this year," he insisted, noting that the two sides have already struck deals on two items of the five-point agenda.

Within Santos' entourage, they say it's also possible an agreement will be reached before the May 25 presidential poll on the topic currently under discussion: trafficking of cocaine, of which Colombia is the world's largest producer.

For many rural Colombians, supported by the FARC, coca -- the plant used to make cocaine -- is the cash crop they survive on.

- 'Enemies of peace' -

Drug trafficking is big business, Santos conceded, for rebels as well as for criminal gangs -- whose numbers, in part, can be traced to former members of rightwing paramilitary groups that sprang up in opposition to the rebels.

"Peace has many enemies: some because they see a political benefit to opposing it, and others because they get rich off the war or because they have gotten illegal advantages, like land they've seized from peasants," the president asserted.

His government has pushed a program aiming to return some two million hectares (five million acres) to 400,000 families -- but many who have tried to benefit, and their representatives, have been killed. The United Nations counted around 30 victims in 2012.

The president's main rival in the upcoming vote is likely to be his predecessor, Alvaro Uribe.

The conservative former leader, who has pushed a hardline policy against the FARC, is now a senator and is focusing his campaign on fighting "impunity" for the rebels -- a sensitive issue in Colombia.

"Justice should support and not be an obstacle to peace," responded Santos, who advocates measures that include the possibility of suspending jail terms in exchange for confessions.

But he adds what he calls an "indispensable clarification:" "there will be no impunity for crimes against humanity or systematic war crimes."