"The only thing missing is Colombia's authorisation," he said in Caracas on Wednesday, appealing for Bogota's "cooperation" to release the hostages.
"We have different options for a secret release but we do not want that, it is very risky," Chavez said.
He added that he hoped that all other hostages held by the Farc, including Betancourt, would also be released.
Theresa Bo, reporting for Al Jazeera from Caracas, said the Farc wanted to release the hostages in a way that would benefit Chavez as much as possible.
Talks between the Farc and Alvaro Uribe, Colombia's conservative president, over the conditions under which the three would be released.
|Clara Rojas is among those hoping to be|
freed in the coming days [AFP]
Chavez was told by Uribe last month to stay out of hostage negotiations with Farc, but he has continued to talk to the rebels.
The Farc, a self-proclaimed communist revolutionary group, said a week ago they would free three hostages: Clara Rojas, her son Emmanuel, who was born in captivity from her relationship with a Farc fighter, and Consuelo Gonzalez de Perdomo, a Colombia legislator.
Ivan Rojas said in Colombia that he supports Chavez's plan to secure the release of his sister.
"We are very optimistic that this will turn out well," he said.
Rojas has been a captive since 2002, when she was seized alongside Betancourt as she campaigned for president.
Perdomo was kidnapped in 2001.
The Farc is Colombia's largest rebel army with about 17,000 fighters and was established in the 1960s as the military wing of the Colombian Communist party.
It is believed to be holding at leats 750 hostages.
The group has previously offered to release 47 high-profile hostages, including Betancourt and three US defence contractors, in return for the release of hundreds of rebels held in Colombian and US prisons.