Colombia's second-biggest leftist rebel group, the National Liberation Army, would be willing to declare a cease-fire if peace talks to end 50 years of war with the government begin, it said in a video posted on its Twitter account on Wednesday.
The 1,500-strong group, known as the ELN, has been engaged in secret exploratory talks with the government for months to draw up terms that may lead to formal negotiations. If they go ahead, the insurgents may cease attacks against government and civilian targets.
"The government has said it wants to end armed conflict. ... We have assisted in dialog to examine the real will of the government and if at the end of the analysis we conclude that arms are no longer necessary, we are ready to consider giving them up," the ELN said in a video message.
The government is already in negotiations with the Revolutionary Armed Forces of Colombia (FARC), the nation's biggest rebel movement, to end a conflict that began in 1964.
War with the two Marxist insurgent groups and right-wing paramilitaries has killed almost a quarter of a million people over the past five decades. Though kidnapping now relatively rare, both groups regularly attack Colombia's oil pipelines.
A U.S.-backed military offensive and expanded intelligence work that began in 2000 helped push the groups deeper into jungle and mountain terrain, damaging communication networks and making it more difficult to launch large-scale attacks.
While Santos has refused to let up his offensive against either rebel group until a peace deal is signed, the ELN's offer to down weapons during talks may be evidence of how serious it is about ending its struggle.
The FARC just weeks ago called an indefinite cease-fire while talks are underway.
"Santos' government has a dilemma of persisting with the policy of war and pacification or dare to take a true path to peace," the ELN said of the government's refusal to call a ceasefire.
The ELN is considerably smaller than the Marxist FARC rebels, which have some 8,000 fighters. The founders of the ELN -- a group of radical Catholic priests -- were inspired by the Cuban revolution of 1959, while the FARC's uprising was guided by the ideology of the Soviet Union.
The two groups, both formed in 1964, have battled a dozen governments were once rivals and fought each other but in recent years have forged alliances. The ELN operates mainly in northeastern Colombia and is headed by Nicolas Rodriguez.
Both groups are considered terrorist groups by the United States and the European Union.
The ELN has sought peace before, holding talks in Cuba and Venezuela between 2002 and 2007 under former President Alvaro Uribe. Experts say there was a lack of will on both sides back then to agree a final peace plan.