By Hugh Bronstein BOGOTA, July 31 (Reuters) - A man who has walked across much of Colombia, hands chained to protest the kidnapping of his soldier son, now plans to camp out in Bogota's main square until there is a hostage exchange with leftist rebels. Gustavo Moncayo has become a hero to thousands of families of kidnap victims since he started his hike across Colombia in June, calling for a swap of rebel hostages for guerrillas held in government jails. His son, Pablo Emilio, was captured when guerrillas from the Revolutionary Armed Forces of Colombia, or FARC, attacked an army post in 1997, shortly before his 19th birthday. Moncayo has heard nothing of him for more than four years. Nearing the end of a 500-mile (800-km) trek from near the border with Ecuador, he vowed on Tuesday to continue his protest by living in Bogota's Plaza de Bolivar just yards (metres) from the presidential palace and the Congress building. "I will do whatever is necessary for my son and for peace in Colombia," said Moncayo, who was expected to reach the capital on Wednesday. Among the scores of politicians, police and soldiers held in secret jungle camps are three U.S. defense contractors captured in 2003 and French-Colombian Ingrid Betancourt, seized by the FARC during her 2002 presidential campaign. President Alvaro Uribe, popular for cutting crime as part of his crackdown on the guerrillas, refuses FARC demands that he demilitarize a New York City-sized rural area to set the stage for hostage swap talks. Thousands are killed in Colombia's war every year while tens of thousands are forced from their homes by violence. The country's problem with kidnapping was brought to the forefront last month when 11 provincial lawmakers were killed while being held in a FARC prison. The deaths prompted hundreds of thousands of outraged Colombians to take to the streets this month, protesting the FARC's use of kidnapping in its 4-decade-old insurgency.