Members of Colombia's second-largest rebel group have arrived in the Cuban capital to hold preliminary peace talks with the Colombian government.
Galan was allowed to leave jail to convince the ELN to begin talks
A spokesman for the left-wing ELN said the meeting in Havana represented a big step in the search for peace.
The aim of the talks is to pave the way for a fully-fledged process to end the long-running conflict in Colombia.
A similar attempt in Cuba two years ago collapsed after a failure to agree on a framework for negotiations.
Rebel representatives from the National Liberation Army (ELN) and the Colombian authorities will hold several preparatory meetings throughout the week, ahead of the opening of formal exploratory talks on Friday.
Diplomats from Spain, Norway and Sweden are expected to attend.
The ELN and the larger Revolutionary Armed Forces of Colombia (Farc) have been involved in a 40-year conflict with state forces and right-wing fighters.
The government delegation is led by the country's high commissioner for peace, Luis Carlos Restrepo.
Mr Restrepo is expected to meet a number of leading ELN members, including the group's military commander, Antonio Garcia.
"We are convinced of the importance of this moment for the country to search for peace", ELN spokesman Francisco Galan told a news conference.
Galan is serving a 30-year sentence for rebellion, terrorism and kidnapping.
But the government allowed him to leave jail for three months in September in the hope that he would convince the rebels to begin talks.
The ELN has been active since 1964 and is believed to have 4,000 members.
Colombian President Alvaro Uribe has already started a peace process with the country's main right-wing paramilitary group, the United Self Defence Forces of Colombia (AUC).
Earlier this week, at least 2,000 combatants and a key leader of an AUC faction surrendered their weapons.