Colombian Marxist rebels have freed a soldier captured a month ago in what they called a peace gesture aimed to pave the way toward an exchange of about 70 hostages for guerrillas held in jail.

The Revolutionary Armed Forces of Colombia said in an e-mailed communique dated July 15 but received on Friday that they had released Duverney Orozco, captured during an assault on the jungle village of Teteye on June 25, when rebels killed 21 soldiers.

The army confirmed it had received Orozco, and said it had sent him for medical and psychological assessment. The date of his release was not clear.

The insurgent force known by the Spanish initials FARC said it acted after meeting a French government emissary to discuss a possible exchange of jailed rebels for about 70 hostages including former presidential candidate Ingrid Betancourt -- a dual French-Colombian national -- and three Americans.

"In response to the work by the French government, with the mediation of the International Committee of the Red Cross, we are freeing the soldier Duverney Orozco, safe and sound," the FARC said.

"This new unilateral peace gesture by the FARC is more undeniable proof of our political will to obtain the prisoner swap denied by the government of (President Alvaro) Uribe," it said.

So far, chances of a deal have looked remote, with the rebels refusing to promise Uribe that if he released any of the thousands of their comrades held in jail, they would not return to insurgent ranks. Late last year, Uribe ordered the extradition of a senior FARC commander to the United States after the guerrillas defied an ultimatum to free their hostages.

The hostages also include policemen, soldiers, politicians and three U.S. Defense Department contractors captured when their light aircraft crashed on a narcotics reconnaissance mission in 2003.

The FARC seized Betancourt in a dangerous part of rural southern Colombia when she was campaigning for president for a small left wing party in early 2002.

The hostages are being held in secret jungle camps. Rebels killed 10 of their prisoners during a botched rescue attempt by Colombian troops in May 2003.

Army commander Gen. Reinaldo Castellanos said the release of Orozco was not a peace gesture and army spokesman added that the rebels blew up a bridge and attacked an oil pipeline in the southern province of Putumayo on Thursday.

"This another act of arrogance by the FARC and not a humanitarian gesture. And it's what they should do with the rest of their hostages," Castellanos said, quoted in newspaper El Tiempo.

The government holds about 4,000 members of the FARC in jail and estimates another 13,000 rebels are hiding out in jungles and mountains waging a 41-year-old war for socialist revolution. The conflict claims thousands of lives a year.