The former Colombian presidential candidate, Ingrid Betancourt, spoke of her "living death" as a hostage of the Farc guerrillas in a moving letter released at the weekend.
Mme Betancourt, 45, who has joint French and Colombian nationality, is one of hundreds of captives believed held by the ultra-leftist guerrillas in the Colombian jungle.
Almost six years after her capture, and four years since the last proof that she was still alive, Mme Betancourt and three American hostages were seen on videotapes captured by the Colombian military last week.
A letter from Mme Betancourt, also captured by the Colombian authorities, was released by members of her family in Paris at the weekend.
"Here, we are living like the dead," Mme Betancourt said in the letter, addressed to her mother. "I no longer have the same strength. It is very difficult for me to continue believing ... I am not well physically ... My appetite is frozen, my hair is falling out in large quantities."
Mme Betancourt describes the monotony of life in the jungle, constantly moving from camp to camp, forced to stretch and speak as little as possible to relieve a sore neck.
She said, without elaborating, that it is a "problem" to be the only woman among male prisoners, many of whom have been held for 10 years or more.
"Life is not life here, but ... a gloomy waste of time," she wrote. "I live, or subsist, on a hammock stretched between two stakes, covered with a mosquito net and with a tarpaulin above."
Mme Betancourt, from a Franco-Colombian family and married to a French diplomat, was kidnapped by the ultra-leftist, and drug-trafficking, Farc movement while she was a Colombian presidential candidate in 2002.
Colombia encouraged by the French President Nicolas Sarkozy recently enlisted the Venezuelan President Hugo Chávez to intercede with Farc for her release. His mission was suspended two weeks ago after a quarrel with the Colombian President Alvaro Uribe.
The Farc leadership has offered a possible hostage swap for guerrilla captives but insists that Mr Chávez must be involved. The right-wing Colombian President accuses the left-wing Mr Chávez of overstepping his brief by seeking direct talks with the leader of the Colombian army. In a statement at the weekend, President Chávez accused the Colombian and US governments of pulling the plug on the negotiations because they did not want the hostages to be released. Farc had offered to release a group of hostages including Mme Betancourt as a gesture of goodwill, he said. That was now blocked.
The French President telephoned President Uribe on Saturday to urge him to set aside such quarrels and revive hopes of a "rapid, humanitarian" prisoner exchange. M. Sarkozy said the tape showing Mme Betancourt and the other prisoners looking haggard and depressed proved the urgency of the situation. He said that he intended to "redouble" his own efforts to win her release.
The release of the Franco-Colombian hostage's letter on Saturday, to the Associated Press, also caused some controversy. Her mother, Yolanda Pulecio, said that she did not want the letter to be published because that would "violate family intimacy", but other family members decided to release the letter to keep up pressure on the French and the Colombian governments.
All family members were united, however, in calling on President Uribe to act more urgently to take up the Farc offer of a prisoner exchange.
Mme Betancourt's mother, in an emotional interview shown on Colombian television, also begged the Farc leader, Manuel "Sureshot" Marulanda, to keep his promise to release Mme Betancourt and other high-profile hostages as a gesture of good faith.
"I ask Marulanda, I beg him, take advantage of this historic opportunity, make a humanitarian gesture, free those whom you have there, the women and children," Mme Pulecio said.