The new agreement to end 52 years of war was put together in just over a month after the original document was narrowly and unexpectedly defeated in an Oct. 2 referendum for being too lenient on the insurgent group.

The government and the Revolutionary Armed Forces of Colombia (FARC) have been in talks in Havana, Cuba for the last four years, hammering out a deal to end a conflict that has killed more than 220,000 and displaced millions in the Andean nation.

Opposition leader and former President Alvaro Uribe spearheaded the push to reject the original accord and wants deeper changes to the new version. He is furious that Santos will ratify the deal in Congress instead of holding another referendum and has called for street protests and may boycott congressional debate on the new deal.

The signing ceremony marks the six-month countdown for the 7,000-strong rebel movement to abandon their weapons and form a political party.

Many of Colombia's largely conservative residents are outraged because, like the original agreement, the new document offers no jail time for FARC leaders who committed war crimes like kidnappings and massacres, and it allows them to hold political office.

The understated signing in Bogota's Teatro Colon before mostly government and local dignitaries is a far cry from the celebration in September, where the coastal city of Cartagena hosted world leaders and United Nations Secretary General Ban Ki-moon.

Santos, who won the Nobel Peace Prize last month for his efforts to end the conflict with the insurgent group, wants to get the deal in place as quickly as possible to prevent risk to the fragile bilateral ceasefire.

The expanded and highly complex new 310-page document makes only small modifications to the original text, such as clarifying private property rights and detailing more fully how the rebels would be confined in rural areas for crimes committed during the war.

The FARC, which began as a rebellion fighting rural poverty, has battled a dozen governments as well as right-wing paramilitary groups.

An end to the war with the FARC is unlikely to end violence in Colombia as the lucrative cocaine business has given rise to dangerous criminal gangs and traffickers.