Sunday's election pits Colombian President Juan Manuel Santos, 62, who is in favor of a negotiated deal with the rebels, against right-wing opponent Oscar Ivan Zuluaga, who has set seemingly impossible tough conditions for peace talks.

Zuluaga, 55, won a first round of balloting on May 25 with 29 percent of the vote as against 26 percent for Santos, making a runoff necessary under Colombian electoral law.

He accuses Santos, who is nearing a deal that would end five decades of war with the Revolutionary Armed Forces of Colombia (FARC), of selling out to the rebels, claiming that they are on the verge of collapse.

Zuluaga long opposed the peace talks, which were launched 18 months ago in Havana, Cuba, but now says he would continue the negotiations under much stricter conditions. Among other things, he says the insurgents must halt all military activity and that some must agree to go to prison.

He and his mentor, former President Alvaro Uribe, have accused Santos of offering impunity to the rebels. Santos denies this, saying he would not let war criminals go unpunished.

High cost of war

Both Santos and Zuluaga were cabinet ministers under Uribe, who ruled the country with an iron hand from 2002 to 2010 and still wields considerable political influence.

Although Santos has now shown a willingness to talk with the rebels, as Uribe's defense minister he carried out an aggressive military campaign that greatly weakened FARC and killed three of its top leaders.

Social issues will also play an important role in voters' decisions, with more than one third of the country's 47 million inhabitants living in poverty despite economic growth of more than four percent a year.

Santos has emphasized the importance of establishing peace if social welfare is to be improved, saying that the "cost of the war" with FARC is nearly 300 dollars - the minimum monthly wage in Colombia - per second.

tj/hc (AP, AFP)