Mr Nicolas Sarkozy said Ms Betancourt's release was a matter of 'life or death' and urged the leftist Farc guerillas to free her without delay.

Two hostages released by the Farc on Wednesday said she is very ill and being severely mistreated by her captors.

Mr Sarkozy described those new accounts as 'excruciating in their cruelty and barbarism that make one feel sick'.

And he said: 'The Farc must know and understand that the martyrdom of Ingrid Betancourt is the martyrdom of France.'

Ms Betancourt has dual French-Colombian nationality.

The former Colombian presidential candidate has been held hostage for six years, becoming a cause celebre in France.

The French leader, who was speaking on a visit to South Africa, said he is prepared to travel himself to the Colombia-Venezuela border to pick up Ms Betancourt if the Farc, the Revolutionary Armed Forces of Colombia, make that a condition of her release.

'They cannot let this woman die,' Mr Sarkozy said. 'It is a race against the clock... We can wait no longer.'

In November, Colombia released videos seized from rebels that for the first time in years showed Ms Betancourt sitting in the jungle, looking frail and gaunt.

And former Colombian senator Luis Eladio Perez, one of four hostages released by the Farc on Wednesday and flown to Venezuela, said Ms Betancourt was 'physically and morally exhausted' by her jungle captivity.

'She is chained up... surrounded by people who have not made her life pleasant at all,' he said.

Mr Perez said three American defence contractors captured in 2003 were also faring badly, and they would probably remain in captivity unless a Farc leader jailed for 60 years in January has his sentence reduced by United States courts.

Another freed hostage, Ms Gloria Polanco, said Ms Betancourt has hepatitis B and 'is near the end', something her family confirmed.

Mr Sarkozy said he had spoken by phone to Venezuelan President Hugo Chavez and planned to speak yesterday with his Colombian counterpart Alvaro Uribe.

The Farc has proposed trading about 40 captives - including Ms Betancourt and the Americans - for hundreds of imprisoned guerillas.

The rebels have an ideological affinity with Mr Chavez and have turned to him as their preferred facilitator.

And the group on Wednesday repeated its demand for the creation of a demilitarised zone to host negotiations on a prisoner swop.

But Mr Sarkozy urged the Farc not to wait for a hostage deal and to release Ms Betancourt as a 'humanitarian gesture'.

The hostage's daughter, Ms Melanie Delloye, said yesterday that she fears her mother's days are numbered. 'Mother is alive, but I don't know for how long, and I know we have to get her out of there as soon as possible,' she told RTL radio.

ASSOCIATED PRESS