Colombia's government and FARC rebels say they have agreed to end hostilities with a definitive ceasefire that leaves the two sides just a step away from resolving the longest-running conflict in the Western Hemisphere.
After more than three years of fraught talks in Havana, the agreement brings into sight an end to a conflict that began as a 1960s peasant revolt before exploding into a cocaine-fuelled war that has killed at least 220,000 people and displaced millions.
The accord will be signed on Thursday in Havana by President Juan Manuel Santos and Revolutionary Armed Forces of Colombia, or FARC, rebel leader Rodrigo Londono, better known by his nom de guerre Timochenko.
"Tomorrow will be a great day! We will work for a Colombia that is at peace, a dream starts to be reality," Mr Santos said on his Twitter feed.
Cuban President Raul Castro, United Nations Secretary-General Ban Ki-moon, Venezuelan President Nicolas Maduro and Chilean President Michelle Bachelet will attend, the two sides said.
The ceremony is expected to be held at 1200 EDT on Thursday.
The ceasefire, which includes terms for the FARC's demobilisation, laying down of arms, and security for former fighters, does not begin until the final deal is signed.
Mr Santos has promised the final accord will be put to the Colombian people in a plebiscite, and must win over those sceptical of FARC promises to rejoin civil society, including supporters of hard-line former president Alvaro Uribe who claims a deal will grant guerrillas impunity for war crimes.
The FARC is particularly concerned about security after its fighters lay down their arms. Thousands of former guerillas were assassinated by paramilitaries after joining a political party during an attempt at peace in the 1980s.
The FARC called a unilateral ceasefire nearly a year ago and the government responded by halting air strikes on rebel camps.
Negotiators missed a self-imposed deadline for signing the final accord in March.
The group of about 8000 combatants, down from 17,000 in its heyday, is considered a terrorist group by the United States and European Union.