Colombia's government and the ELN guerrilla group agreed to a six-month ceasefire in Havana Friday as they work towards a peace pact to end decades of conflict.

A deal for a "bilateral, national and temporary ceasefire," according to Cuban Foreign Minister Bruno Rodriguez, was signed in the presence of Colombian President Gustavo Petro and ELN leader Antonio Garcia.

Rodriguez said the ceasefire -- sealed at the conclusion of a third round of peace talks in the Cuban capital -- would enter into force on August 3.

Founded in 1964, the ELN had more than 5,800 combatants in 2022, according to authorities. It is Colombia's last active guerrilla group.

The ELN has taken part in failed negotiations with Colombia's last five governments, and has been party to only one previous ceasefire which lasted for 101 days in 2017 and 2018.

"Here, a new world is born, here a phase of the armed insurgency in Latin America ends," Petro said at Friday's ceremony.

Garcia, whose presence was made possible by Colombia's top prosecutor scrapping an arrest warrant for him just days earlier, was more cautious.

"We have not yet signed substantial agreements" but rather "procedural agreements," he said.

Dialogue with the ELN started in 2018 under then president Juan Manuel Santos, who had signed a peace treaty two years earlier with the larger Marxist Revolutionary Armed Forces of Colombia (FARC) rebel group.

The FARC subsequently disarmed and transformed itself into a political party.

But talks with the ELN were called off in 2019 by conservative then-president Ivan Duque following a car bomb attack on a police academy in Bogota that left 22 people dead.

Duque had arrest warrants issued for ELN negotiators and asked Cuba to extradite them, which Havana refused. This caused then US-president Donald Trump to add Cuba to a list of countries deemed as sponsors of terrorism.

- 'Total peace' -

Petro, a former guerrilla who last August became Colombia's first-ever leftist leader, reached out to the ELN shortly after coming to power in pursuit of his "total peace" policy.

The two sides resumed formal talks in Venezuela in November for the first time since 2019. A second round was held in Mexico, followed by a third now in Cuba.

A fourth negotiating round will be held in Venezuela from August 14 to September 4, said Rodriguez.

UN Secretary General Antonio Guterres, through a spokesman, congratulated the parties Friday for taking "important steps forward that send hope to the Colombian people, especially the communities who are most affected by conflict."

Guterres, said spokesman Stephan Dujarric, hoped the two sides would work together "in good faith" and noted their request for the UN to play a role in monitoring and verification of the ceasefire.

The ELN had refuted a ceasefire announcement made by Petro on New Year's Eve, and an ELN ambush of a military convoy in March, which left nine soldiers dead, had cast doubt over the future of the talks.

The ELN is primarily active in the Pacific region and along the 2,200-kilometer (1,370-mile) border with Venezuela.

Colombia has continued to be gripped by violence despite the 2016 peace deal, as fighting continues over territory and resources between dissident FARC guerrillas, the ELN, paramilitary forces and drug cartels.

Petro is also attempting to negotiate with these other armed groups.