Colombia’s largest armed rebel organization — the Marxist FARC, or Revolutionary Armed Forces of Colombia — announced Monday that it has met with another rebel group, the ELN (National Liberation Army), to discuss unification of the two organizations, according to the BBC.

Meanwhile, the FARC resumed talks with the Colombian government in Havana Monday, where the two sides clashed over a FARC proposal that Colombia’s 2014 general election be postponed for one year. The FARC says it wants the delay to permit a constituent assembly to decide the country’s political future.

The Colombian government says it will only discuss the agenda already agreed to with the FARC.

Last month, the sides reached agreement on the economic and social development of rural areas and providing land to the people living there.

The ELN — Colombia’s second-largest rebel group — is not participating in the Havana talks but has said it would like to, the BBC reported. The talks have been occurring for more than six months.

The FARC is believed to have approximately 8,000 fighters — half the number it had in 2001. The Colombian government estimates that the ELN has less than 1,500 men.

The Colombian government estimates that since the conflict began in the 1960s, 600,000 people have been killed with three million more displaced by the fighting.