The video is the first proof in more than a year that she is alive

Ingrid Betancourt, a former presidential candidate, delivered her plea in a videotape which was broadcast on Colombian television on Saturday.

The videotape was the first evidence in more than a year that Ms Betancourt was still alive.

She was kidnapped in February 2002, along with her campaign manager, by guerrillas from the Revolutionary Armed Forces of Colombia (FARC).

The guerrillas want a number of rebel prisoners freed in return for Ms Betancourt's release.

'Be careful'

In her message, a haggard and gaunt looking Ms Betancourt said President Uribe alone must decide whether to authorise a rescue mission.

I support a rescue but only if it's going to be well-planned Juan Carlos Lecompte, husband

"It's important that it be the president who directly makes this decision. I believe it is not a military decision, but a political one," she said.

President Uribe told reporters Ms Betancourt's plea "is something the government must handle very carefully, which the defence ministry has to analyse.

"I believe that the government's only response is, be careful," he said.

The danger of trying to rescue hostages was highlighted in May of this year, when FARC guerrillas killed 10 captives as government soldiers closed in on them.

Rescue fears

Ms Betancourt's family has consistently opposed mounting a rescue mission, but Defence Minister Marta Lucia Ramirez said the video might change their minds.

"I believe that with this statement from Ingrid we will have the opportunity to have discussions with her family... which will in the future permit us to rescue her," he said.

Ms Betancourt's husband, Juan Carlos Lecompte, said he was now in favour of a rescue attempt.

"I support a rescue but only if it's going to be well-planned," he said.

Ms Betancourt's mother, Yolando Pulecio, said she was afraid a rescue attempt might end in failure.

"She is very brave, but to me, a mother, a rescue terrifies me," she said.

Ms Betancourt is one of the most high-profile of about 850 captives held by the FARC.