BOGOTA, Sha'ban 17, 1435, Jun 15, 2014, SPA -- Colombians vote on Sunday in the tightest presidential election in decades, a contest that will decide if the nation moves ahead on peace talks with Marxist FARC rebels or step up its battlefield offensive, Reuters reported. President Juan Manuel Santos, who has cast the election as a choice between peace and war, faces right-wing challenger Oscar Ivan Zuluaga, a skeptic of talks, who nudged ahead of the incumbent in last month's first-round ballot. The candidates are locked in an unpredictable race, that polls show is too close to call and may have the narrowest margin for 20 years. Santos, 62, began talks with the Revolutionary Armed Forces of Colombia (FARC) to end a conflict and has made the pursuit of peace the centerpiece of his campaign. He announced this week that preliminary talks had begun with the nation's second biggest insurgent group, the National Liberation Army. --SPA 11:42 LOCAL TIME 08:42 GMT www.spa.gov.sa/w