"In the coming days, (President Juan Manuel) Santos will announce the start of negotiations with the FARC, which will be opened in Oslo October 5th and will continue in Havana," said Santos, who is a cousin of the president but critical of many of his policies.
Norway's foreign ministry declined on Monday to comment on reports that Oslo would host the initial talks.
Colombian media were treating what would be a landmark development toward ending decades of civil strife as a done deal.
But the president himself has not commented on reports of government contacts with the Revolutionary Armed Forces of Colombia (FARC) to lay the groundwork for a peace process, the first in Colombia in a decade.
One key member of his team, chief prosecutor Eduardo Montealegre, acknowledged on Monday that Colombia "must move toward a peace process."
"The end of fighting in Colombia won't be brought about with arms," he told W radio. "Putting this decades-old conflict behind us will be achieved with a peace process. We all deserve peace; it is a constitutional right."
Daniel Garcia-Pena, who was peace commissioner from 1995-1998 under ex-president Ernesto Samper, also sounded positive about the outlook.
"If the contacts are confirmed, I am upbeat. I think both the government and the FARC understand that continuing the war is senseless," he said.
"The rebels have known for some time now that they are not going to take power in a war, and that they are going to have to become a (legal) political force if they are going to survive in a postwar atmosphere," Garcia-Pena said.
And the government "knows ending the conflict is central to its success in being able to make Colombia part of the world of major democracies," he stressed.
Founded in 1964, the Marxist-inspired FARC — Latin America's largest and longest-fighting insurgency — is believed to have some 9,000 fighters, most of them hiding out in mountainous and jungle areas.
Through mediation by former senator Piedad Cordoba and the International Committee of the Red Cross, the FARC has released dozens of hostages since 2008, most of them police officers or troops captured during clashes.
The FARC renounced the practice of kidnappings for ransom in February but has stepped up attacks on Colombian security forces over the past year in remote parts of the country.
The group released its last 10 military and police hostages in April, but is believed to still be holding dozens of civilians.