Colombia's Farc rebels have declared a unilateral ceasefire for an indefinite period, starting from Saturday.
The leftist rebels said the truce should become a formal armistice and would only end if they were attacked.
The announcement was made in Cuba, where the Farc has been holding peace talks with the Colombian government.
President Juan Manuel Santos has so far refused to suspend military action, saying the rebels would use a bilateral truce to rearm and regroup.
The peace talks in Cuba - which began in 2012 - are aimed at ending five decades of conflict that has killed an estimated 220,000 people.
"We have resolved to declare a unilateral ceasefire and end hostilities for an indefinite period of time, which should be transformed into an armistice," the Farc said in a statement.
Colombia's largest rebel group had previously called for a bilateral truce - but these moves have been rejected by the government in Bogota.
The peace talks were almost derailed in September after the Farc captured Gen Ruben Dario Alzate, prompting President Santos to suspend the negotiations.
The rebels released the general unharmed in November in an effort to revive the talks.
But following Wednesday's announcement by the Farc, President Santos may come under renewed pressure now to match the rebel offer, BBC regional analyst Leonardo Rocha says.