Colombia has offered to suspend the sentences of jailed guerrillas if rebels first free hostages including former presidential candidate Ingrid Betancourt.

Peace Commissioner Luis Carlos Restrepo said late Thursday that the liberation of some captives could jump-start the process of exchanging guerrillas for dozens of hostages, including three U.S. defense contractors.

"It is enough that Ingrid Betancourt be immediately freed for us to consider this humanitarian exchange is moving forward, and to begin delivering the benefits of suspended sentences to (jailed) members of the guerrilla group," Restrepo told reporters.

In return for the hostages' release, rebels would have to promise not to return to the ranks of the Revolutionary Armed Forces of Colombia, or FARC, which has been fighting for decades to topple the government.

Family members of Betancourt, a French-Colombian citizen who has spent more than six years as a hostage in the jungle, are increasingly raising concerns over reports of her failing health. Betancourt's husband, Juan Carlos Lecompte, has warned that she has "just months" left to live.

Her ex-husband, Fabrice Delloye, said the Colombian government's offer represented "a positive step — the first time the Colombian government is talking about Ingrid's release and also the opportunity for a humanitarian agreement."

But he said it was still "just a step."

"Restrepo must be more specific ... telling FARC, we are ready to talk to you, we are ready to make a humanitarian agreement through a meeting in a free zone or a demilitarized zone in the southwest of Colombia," he told The Associated Press in France.

The government said earlier Thursday it had received reports that Betancourt is dangerously ill, suffering from Hepatitis B and the skin-eating disease lesmaniasis.

"We hope from this moment on that the loud national and international clamor for Ingrid Betancourt's liberation can lead us in the fastest way possible to her freedom," Restrepo said following a meeting with President Alvaro Uribe.

The FARC has demanded the government create a demilitarized zone in southwestern Colombia as a site for talks, but Uribe has consistently rejected the idea.

The rebels released several hostages earlier this year to missions led by Venezuelan President Hugo Chavez and the International Committee of the Red Cross. But the FARC has been quiet about a possible prisoner swap since March 1, when Colombian troops killed its chief spokesman and 24 others in a bombing raid in neighboring Ecuador.

Also Thursday, Mexico's government said it has asked Colombia to compensate families of four Mexican students killed and another wounded in the raid.