By Monica Garcia and Peter Murphy
BOGOTA (Reuters) - President Juan Manuel Santos called on Monday for the smaller of Colombia's two leftist rebel groups, the ELN, to join the larger FARC guerrillas in declaring a unilateral ceasefire as peace talks advance to end a 50 year war.
The government has been in exploratory talks with the National Liberation Army or ELN, aiming to start negotiations similar to the two-year-old talks under way in Cuba with the FARC.
"We wish to invite the ELN to join this initiative of a unilateral ceasefire like the FARC has done and invite them to reach an agreement as soon as possible on the agenda points we have been discussing for some time," Santos said in a statement.
The government and the ELN announced last June in a joint statement that they have been meeting in secret to agree on the agenda of eventual negotiations.
Santos said back then that the talks would be held under the same conditions as those with the FARC, or Revolutionary Armed Forces of Colombia, in a foreign location and without a ceasefire by government forces.
ELN numbers are now estimated at around 3,000 and FARC has about 8,000. The ranks of both groups have been roughly halved by a decade-long U.S.-backed military offensive.
Optimism over the peace process with the FARC has grown in the last few weeks after it released a kidnapped army general and then declared an unlimited unilateral ceasefire from Dec. 20 while also making a number of conciliatory statements.
Santos, who has been meeting for three days with the government team negotiating with the FARC and foreign experts on peace negotiations, said he recognized that the FARC have so far been holding to their ceasefire.
The group has threatened to call off the ceasefire however, if the government attacks. The government has refused the FARC's demands for a ceasefire on both sides.
(Additonal reporting by Helen Murphy; Editing by Grant McCool)