Nicolas Sarkozy, the French president, has called on Colombia's Farc rebels to release Ingrid Betancourt, the French-Colombian hostage held by the group, saying she is close to death.
"Ingrid is in danger of imminent death," he said in speech addressed to Manuel Marulanda, the Farc leader, and broadcast on French television on Tuesday.
"You, who lead the Farc, you have a rendezvous with history. Don't miss it. Free Ingrid Betancourt and the weakest hostages," Sarkozy said.
Betancourt, a former Colombian presidential candidate, has been held for more than six years and is said to be suffering from hepatitis B.
In the highly personal message, Sarkozy said Marulanda had "a rendezvous with history" and would have a crime on his hands if she died.
His brief appeal was also subtitled in Spanish.
Francois Fillon, the French prime minister, said France would be willing to take in former rebels as part of a possible deal to free Farc hostages, including Betancourt.
A spokesman for Sarkozy said at the weekend that a plane with medical supplies would be kept on standby in France ready to intervene "at any time" if a hostage deal could be reached.
The Colombian government has also offered a prisoner exchange in order to secure the release of Betancourt and other hostages.
The Farc (Revolutionary Armed Forces of Colombia) is holding hundreds of hostages as part of what it has said is a Marxist armed struggle against the Colombian government.