Colombian President Alvaro Uribe was booed on Thursday by a crowd demanding changes in his approach to attaining peace in the South American country, according to dpa. But Uribe defended his hardline stance against left-wing rebel groups in front of the hostile crowd in the capital Bogota, saying he would not give in to the rebels' demands for a demilitarized zone in parts of the country to promote dialogue. "I will not give a square kilometre to criminals. This country was demilitarized for many years, which is why the guerrillas and the paramilitaries took it," Uribe said in a speech on the city's Bolivar Square. Uribe's speech came after he met for more than two hours with Gustavo Moncayo, the father of a soldier kidnapped nine years ago by the largest left-wing rebel group, Revolutionary Armed Forces of Colombia (FARC). Moncayo had walked some 1,000 kilometres across the country for 46 days to promote an exchange of rebels for hostages held by FARC. He arrived in Bogota Wednesday and set up a tent just off the square. Uribe said he was willing to free FARC rebels held in Colombian prisons if the leftist group frees all the kidnapped. Only once that happened, "with the participation of the international community, the government accepts a meeting area for 90 days to agree on peace with FARC." Moncayo said it was up to Uribe and FARC to agree on a way forward. "The president has made two proposals, but it is not up to me to accept them. I am just a mediating element. Those proposals have to be explained to the other party, and let's see what they reply," Moncayo said. FARC have been fighting the government in Colombia for more than 40 years. They hold, among others, a group of more than 50 politicians and military personnel - including former presidential candidate Ingrid Betancourt. Efforts to arrange an exchange have failed as Uribe has refused to meet the rebels' demand to demilitarize two towns in south-western Colombia for negotiations.