PARIS France said on Friday it was still waiting for a response from Colombian FARC guerrillas about its mission to aid hostage Ingrid Betancourt, a French-Colombian politician held since 2002.
"We have tried everything," French Foreign Minister Bernard Kouchner said in an interview on Europe 1 radio.
"We've got the whole of Latin America moving and they're now involved," he said. "We're waiting, we're in place."
A French medical team arrived in Colombia on Thursday, despatched by President Nicolas Sarkozy in a bid to treat Betancourt, who is believed to be seriously ill after more than six years of captivity in the rebels' jungle stronghold.
"We're trying, trying, trying and there's no other solution," Kouchner said.
Sarkozy has made the release of Betancourt, a former Colombian presidential candidate, a foreign policy priority, but so far few details have been revealed about the mission to try and treat her in the rebel camp.
In a statement, FARC leader Rodrigo Granda said the killing of a senior commander in March complicated hostage negotiations and rebels would not free Betancourt or any captives without a deal to exchange them for jailed rebels.
Granda did not refer directly to the Betancourt mission or make clear if it would be allowed to visit captives.
A French diplomat said on Friday that Granda's statement predated the latest effort to reach Betancourt.
"Granda's letter was published on March 19, well before the humanitarian mission was even envisaged," said the diplomat, who spoke on condition of anonymity.
The French aircraft was waiting on the tarmac at Bogota's Catam military air base, fuelled and ready to fly to anywhere it was required inside Colombia, officials said.
Betancourt's son made an emotional plea on French radio station RFI, telling his mother he was doing well in school and appealing to her captors to free her.
"To the FARC, please make a gesture. Understand that this is a historic moment for you," Lorenzo Delloye Betancourt said in remarks translated from Spanish.
"Mamita, I know you're going through very difficult times, but please, these are really the last of those days... We all want to see that strong, gutsy woman you are again," he said.
Captives freed in recent months by the rebels in deals brokered by Venezuelan President Hugo Chavez say Betancourt is very ill with hepatitis. Images from a rebel video released last year showed her pale and gaunt in a hidden jungle camp.
Freed hostages say she has been chained to a tree after several attempts to escape.
(Reporting by James Mackenzie, Evelyn Sayan, Brian Rohan and Francois Murphy; Editing by Matthew Jones)