Venezuelan President Hugo Chavez has held fresh talks with high level representatives of the Colombian left-wing rebel movement, the Farc.
The meeting involved Ivan Marquez, an envoy of the Farc leader Manuel Marulanda, and was held in Caracas.
Mr Marquez said if Mr Chavez and Mr Marulanda could meet it would remove some obstacles to a prisoner swap.
Mr Chavez said such a meeting was on the agenda, but a time and place had not yet been decided.
"Today I'm more optimistic than ever over this humanitarian exchange issue," Mr Chavez said.
Mr Marquez said a future meeting could possibly take place in Colombia's El Yari region, where Mr Marulanda is thought to be hiding out, in the jungle near Colombia's borders with Venezuela and Brazil.
Colombia gave its blessing to Mr Chavez's talks, in an effort to secure the release of around 50 high-profile prisoners being held by the Farc, but has not authorised a meeting on Colombian soil.
The Farc wants 500 rebel prisoners freed in exchange for the hostages who have been held for years in jungle camps.
They include French-Colombian citizen and former presidential candidate Ingrid Betancourt, and three US defence contractors.
Mr Chavez said Farc fighters had been ordered to give proof that the hostages are still alive.