By Nelson Acosta HAVANA (Reuters) – Colombian war victims demanded a bilateral ceasefire to halt Latin America’s longest running conflict on Wednesday in a direct challenge to President Juan Manuel Santos, who has resisted rebel calls for a ceasefire during peace talks. Victims from all sides in Colombia’s 50-year-old war recently began addressing government and rebel negotiators in peace talks, which have been held in Cuba for nearly two years. In those 22 months, the armed forces and leftist guerrillas have engaged in periodic combat. On Wednesday a group of 12 victims asked the Colombian military and leftist guerrillas of the Revolutionary Armed Forces of Colombia (FARC) to lay down their arms while continuing to talk.