"We have resolved to declare a unilateral ceasefire and end hostilities for an indefinite period of time, which should be transformed into an armistice," said the leftist rebels' peace negotiators in Cuba yesterday, where they are in talks with the Colombian government to end the 50-year war.
"This unilateral ceasefire, which we hope will last a long time, will end only if our guerrilla units have been the object of attacks by the security forces."
The FARC have repeatedly called for a bilateral ceasefire as part of the ongoing peace process.
The peace talks were thrown into crisis last month when the FARC captured an army general, causing Santos to suspend negotiations.
The rebels defended the capture as a legitimate act of war, but released the general on November 30 in order to revive the peace process.
The Colombian conflict has killed more than 2,20,000 people and uprooted 5.3 million since the Revolutionary Armed Forces of Colombia (FARC) was founded in the aftermath of a peasant uprising in 1964.