CARACAS, Venezuela (CNN) -- Venezuelan President Hugo Chavez and a top Colombian guerrilla chief Thursday gave a glimmer of hope that dozens of hostages held by the leftist rebels would be freed.
Venezuela's Hugo Chavez is seen with FARC's Luciano Marin Arango and Colombia Sen. Piedad Cordoba.
"We've been trying to put the pieces together for a way out," Chavez said at the end of the negotiations at Venezuela's presidential palace. "Today, I'm more optimistic than ever about an exchange."
Chavez, acting on behalf of the Colombian government, held talks beginning Tuesday with Luciano Marin Arango, a member of the high command of the Revolutionary Armed Forces of Colombia (FARC), and Colombian Sen. Piedad Cordoba in a bid to broker the exchange of as many as 50 kidnapped civilians.
Established in 1964 as the military wing of the Colombian Communist Party, FARC is Colombia's oldest, largest, most capable and best-equipped Marxist rebel group, according to the U.S. Department of State.
The United States, the European Union and Colombia classify FARC as a terrorist group.
Among the captives are Ingrid Betancourt, a French-Colombian senator who was kidnapped in 2002, and three American contractors who were captured when their plane went down in 2003 during a drug-eradication flight.
The most concrete development to be announced publicly on Thursday was the pledge by the FARC leadership to offer proof the hostages are safe. In August, the rebels released the bodies of 11 Colombian congressmen who had been kidnapped earlier in the summer.
"Comandante Manuel 'Marulanda' Velez has given a direct order to those in charge of the prisoners of war to, as soon as possible, send their respective commanders proof that Ingrid Betancourt and the three gringos and all of the captives ... are alive, so that information can be transmitted to President Hugo Chavez and to Piedad Cordoba," said Marin Arango, who goes by the nom de guerre "Ivan Marquez."
The guerrillas are demanding the release of 500 imprisoned FARC rebels in return for their hostages.
Chavez said he hoped to have that proof in hand on November 20 when he arrives in Paris for a state visit with French President Nicholas Sarkozy, who has expressed particular interest in seeing Betancourt freed.
Chavez also said he expected to discuss the situation with Colombian President Alvaro Uribe when both men attend the Ibero-American Summit Friday in Santiago, Chile.
Marin Arango said a summit between Chavez and Velez, the FARC commander-in-chief, could be the key to overcoming obstacles to an exchange. The rebels see a possible meeting between Velez and a foreign head of state as a public-relations coup for the legitimacy that it would lend them.
Prior prisoner release negotiations between Colombia and FARC have stalled over a rebel demand for creation of a demilitarized zone for the exchange and for released rebel prisoners to return to the guerrilla group. On Thursday, Marin Arango also reiterated the guerrillas' demands for a demilitarized zone. E-mail to a friend