The Revolutionary Armed Forces of Colombia (FARC) offered to release the three lawmakers with the help of leftist Venezuelan President Hugo Chavez and a Colombian opposition senator.
"We ask President Hugo Chavez and Senator Piedad Cordoba that they personally, or through representatives, receive in Colombian territory the lawmakers Gloria Polanco, Luis Eladio Perez and Orlando Beltran," said a guerrilla statement published by Anncol, a news agency close to the rebels.
The FARC said they were releasing the three hostages, who were kidnapped in 2001, "unilaterally because of the state of their health."
For its part the government of Venezuela said Sunday that it would immediately take steps to ensure the safe and sure handover of the three hostages.
"Our government will move forward, beginning this very moment, with the necessary contacts and actions" to free the captives, Chavez spokesman Jesse Chacon said in a statement Sunday.
The three lawmakers are among 43 high-profile hostages, including three Americans and Franco-Colombian politician Ingrid Betancourt, whom the FARC want to exchange for 500 rebels held in Colombian prisons.
The announcement comes a month after the FARC released two hostages -- lawmaker Consuelo Gonzalez and Betancourt's former presidential campaign manager, Clara Rojas -- to Chavez's government and the Red Cross.
The chief of Colombia's military, General Freddy Padilla de Leon, said in a statement that President Alvaro Uribe welcomed any "unilateral releases without conditions."
Padilla added that the FARC announcement was "the first consequence" of demonstrations planned for Monday across Colombia and 125 capitals worldwide to denounce the rebel group.
The FARC, accused of drug trafficking and holding some 750 people hostage, is classified as a terrorist organization by the United States, European Union and Colombian government.
But some relatives of hostages, unions and leftist parties opposed the demonstration, which was spearheaded by a group of young Colombians fed up with the FARC's tactics.
While relatives fear that the demonstrations could provoke the rebels into hurting hostages, leftist groups accuse Uribe's conservative government of trying to gain support for its hardline policies.
"Who will benefit from this march?" Betancourt's mother, Yolanda Pulecio, was quoted as saying in Semana magazine. "Maybe neither the hostages nor the humanitarian exchange or peace will benefit."