Colombia has agreed to back a referendum asking whether it should swap jailed guerrillas for hostages held by the Farc rebel group.
France has campaigned for the release of Ingrid Betancourt
A presidential spokesman said the poll would be held alongside congressional elections in March.
Farc holds more than 60 hostages, including some held for several years.
Analysts say the government hopes the vote will put pressure on the rebels to agree to the swap, which they have so far rejected.
Polls suggest the idea of a deal is supported by most Colombians, and it has the backing of President Alvaro Uribe.
"There is total support for this proposal," Colombian Peace Commissioner Luis Carlos Restrepo said.
"We believe that in this way we can consolidate support for a humanitarian accord as a national proposal."
He said hostages' relatives - not the government - would lead the campaign to support the swap plan.
The hostages include politicians, soldiers and police officers, held in secret jungle locations.
Among them are three Americans and the Colombian-French politician Ingrid Betancourt.
The referendum was announced during a high-level diplomatic visit from French officials, who have offered to mediate and backed the referendum plan.
"An accord will come from a political resolution. In no way will it come from a military operation or from violent means," said France's Foreign Minister Philippe Douste-Blazy during a one-day visit to Bogota, Colombia's capital.
Last month, Mr Uribe agreed to withdraw government troops from a jungle area in southern Colombia to provide a demilitarised zone for negotiations with Farc.