Colombia will resume peace talks with the FARC Wednesday amid rising tensions after government forces killed at least 20 rebels and President Juan Manuel Santos issued a 12-month deadline.
The dialogue is being held in Cuba and is the fourth attempt to end a conflict that has lasted almost half a century, leaving 600,000 dead, 15,000 missing and four million displaced.
The FARC delegation has accused the government of "political incongruity" for refusing to join the leftist rebels in declaring a ceasefire during the latest peace effort, which is restarting in Havana after a five-day break.
FARC negotiator Andres Paris suggested that the government was not doing enough to pursue peace, and said that although there had been some rebel violence, the incidents were minor.
"The government is showing signs of political incongruity and its response to the FARC's gesture is bellicose," he told Cuban state media.
Santos upped the stakes with the FARC on Sunday, when he warned that the peace process should take months, rather than years, and said an agreement to end hostilities should be reached by November 2013.
Lead government negotiator Humberto de la Calle meanwhile demanded in Bogota that the FARC clarify their position on abductions, before heading to Cuba to resume the talks.
"The FARC have to answer to the victims. They have to clarify the kidnapping problem," the former vice president stressed in a message to media at the presidential palace.
The Revolutionary Armed Forces of Colombia formally started talks with Bogota on October 18 in neutral Norway. The negotiations moved to Havana on November 19. Both sides cited progress last week after that round.
But the military's bombing early Saturday of three rebel camps in Narino province, near the border with Ecuador, rattled the calm. The army said 20 rebels were killed.
Three previous peace attempts have failed. In the last effort, which lasted from 1999 to 2002, the government ended talks after concluding that the FARC were using a vast demilitarized zone to regroup.
The FARC -- founded in 1964 and believed to have around 9,000 fighters -- took up arms to protest against the concentration of land ownership in Colombia, which is seen as the defining issue of the peace negotiations.
The rebels have suffered a string of military defeats in recent years, and several of their top commanders have been captured or killed.