The Colombian government and rebel group FARC have reached a deal on a bilateral ceasefire that would be the last major step toward ending one of the world's longest wars.
Colombia's conflict has killed more than 220,000 people and displaced millions since 1964. But a 15-year, US-backed military offensive has depleted the rebels' ranks and forced its ageing leaders to the negotiating table in 2012.
President Juan Manuel Santos will travel to Cuba on Thursday for the announcement with the Revolutionary Armed Forces of Colombia, or FARC.
Both sides in January tasked the UN with monitoring adherence to an eventual ceasefire and resolving disputes emerging from the expected demobilisation of at least 7,000 armed rebels.
The peace talks have been bumpy and lasted much longer than expected.
If a final deal is reached it would bring an end to Latin America's last major insurgency, one that is accused of being a major supplier of cocaine to the US.
Mr Santos said this week he hoped to agree a final deal by July 20, when Colombia celebrates its declaration of independence from Spain
Once a deal is reached, it must also face a planned referendum where Colombians will be asked for their endorsement.
Opinion polls show the FARC are disliked among conservative Colombians and frustration has been growing the longer the talks have dragged out.