Updated

Colombians will choose between a leftist former guerrilla and a young conservative lawmaker in a presidential election to decide who will lead the nation as it implements a still-fragile peace accord.

One-time militant and ex-Bogota mayor Gustavo Petro and frontrunner Ivan Duque harbor contrasting views on the accord ending Latin America's longest-running conflict and could significantly shape how Colombia proceeds with putting aspects of it into motion.

Petro is vowing to uphold the accord while Duque wants to make changes like requiring ex-combatants to serve time before entering politics if they are guilty of crimes against humanity. Under the agreement, rebels who fully confess and offer reparations to victims are unlikely to be sent behind bars.

Sunday's election will be the first presidential vote since the signing of the accord.