A former presidential candidate held by leftist rebels describes in an emotional letter how she has lost her hair, appetite and hope after nearly six years constantly on the move in Colombia's jungles.

The letter, along with videos released by government officials Friday, were the first evidence in years that Ingrid Betancourt and other rebel-held hostages including three U.S. military contractors may still be alive.

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The materials were seized during the arrest in Bogota of three suspected members of the Revolutionary Armed Forces of Colombia, or FARC.

"Here, we are living like the dead," Betancourt writes to her mother. The dual French national was kidnapped in February 2002 while campaigning for the presidency.

An outspoken former anti-corruption lawmaker, Betancourt sounds resigned and weakened in the 12-page handwritten letter, which is dated Oct. 24. Excerpts were released to The Associated Press in Paris by people close to her family.

"I no longer have the same strength, it is very difficult for me to continue believing," she writes. "I am not well physically ... My appetite is frozen, my hair is falling out in large quantities."

A short videotape released with the letter shows grainy images of an extremely gaunt Betancourt staring at the ground, rosary in hand.

In an interview with the left-wing Bolivarian press agency released Saturday, a FARC commander said that following the captures, the rebels for now will not release further evidence the hostages are still alive.

"Bogota's folly forces the FARC to take drastic actions because it cannot run the risk that other emissaries will be detained," said Marin Arango, who uses the nom de guerre Ivan Marquez. He met recently with Venezuelan President Hugo Chavez in Caracas for talks on a possible deal to swap rebel-held hostages for imprisoned guerrillas.

"We are profoundly sorry that all the families won't receive proof of life of their loved ones for Christmas, as we had hoped."

Each of the three Northrop Grumman Corp. contractors, who have been held since their surveillance plane went down in February 2003 in rebel territory, also appear in videos.

In the letter, Betancourt describes stretching to relieve her sore neck, speaking as little as possible, and says it is a "problem" to be the only woman among several male prisoners, some of whom have been held for a decade.

Betancourt describes her joy in hearing her mother and other supporters send her messages through a jungle radio station. She appeals to her daughter and son, who live in France, to send three messages a week even though she can't respond. And she urges the children to get doctoral degrees.

"Life is not life here, but ... a gloomy waste of time," she writes. "I live, or subsist, on a hammock stretched between two stakes, covered with a mosquito net and with a tarp above, which works as a roof and allows me to think I have a house."

She describes a trying life of frequent movement.

"At any moment they give the order to pack up and I live in all kinds of holes, like any kind of animal," writes Betancourt, who will turn 46 on Christmas. "The marches are a burden because my equipment is very heavy and I can't manage."

The families of Betancourt and the other hostages welcomed the proof their loved ones were still alive but expressed frustration at the lack of progress toward their release. Some blamed President Alvaro Uribe, who has said he would prefer to rescue them in military operations.

Betancourt's letter expresses hope in mediation efforts by Venezuela's Chavez, President Nicolas Sarkozy of France and the U.S. President George W. Bush.

The U.S., French and Colombian governments had demanded evidence the captives were alive during Chavez's mediation effort to win the release of 46 high-profile hostages held by the FARC.

Uribe abruptly ended Chavez's mediation role on Nov. 21, claiming that the Venezuelan president had overstepped his bounds by directly contacting the head of Colombia's army.

The rebels confirmed the videos and letters were destined for Venezuela.

"The proofs were going to President Chavez, and the Colombian government knew it," Marquez said, adding that Chavez "with all certainty was going to find a definite solution to the humanitarian drama of prisoners held by both sides.

"With Uribe acting this way, there will never be an exchange," he said.

On Saturday, Sarkozy spoke by telephone with Uribe and expressed concern about "the obvious precariousness" of Betancourt's health and "about her despair," his office said in a statement. He urged Uribe to act urgently to pursue a hostage swap.

Marquez said the FARC would welcome Sarkozy's possible intervention in any future negotiations.

Betancourt's mother, Yolanda Pulecio, told the AP that she did not want the letter released publicly. She said she had received it from the chief prosecutor's office and that its release "violated the family's intimacy."