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.
Rojas has been a captive since 2002, when she was seized along with French-Colombian politician Ingrid Betancourt as she was campaigning for president. Perdomo was kidnapped in 2001.
According to a Farc statement, the three are to be released to Hugo Chavez, Venezuela's president, or someone he designates.
They are among 45 prominent hostages Farc wants to swap with the Colombian government for its about 500 imprisoned members.
As hopes that the hostage release would take place in time for Christmas dimmed, some of their relatives planned delayed celebrations.
Patricia Perdomo, Gonzalez' daughter, said: "This is not Christmas Eve for my family. Our Christmas Eve will be the day we're reunited ... We're hoping my mom will be with us by Christmas.
"Only when she's here will [we] be opening gifts and celebrating."
Betancourt's husband Juan Carlos Lecompte hoped his wife could see her two children for Christmas in photographs. He dropped 22,000 of them from a small plane he rented and flew on the weekend over a jungle near Brazil, where she's thought to be held.
Each photo was signed "for Ingrid from Juan Carlos". Betancourt turns 46 on Christmas Day.
Alvaro Uribe, the Colombian president, on Monday wished Christmas greetings to the three yet-to-be-freed hostages and all other captives held by Farc.
"I want this Christmas greeting to reach the hostages, along with the hope they will soon be released," Uribe said in a speech to a military unit in northern Magdalena department.
"On this Christmas, I send my greetings to the families of the 750 people Farc has kidnapped over the past 10 years."