Colombia's Government and the Revolutionary Armed Forces of Colombia (FARC) guerrilla force have agreed on a definitive ceasefire, taking one of the last steps towards ending Latin America's longest civil war.

The announcement heralds an end to a half-century conflict that has killed hundreds of thousands of people in the jungles of the major cocaine-producing country.

"We have successfully reached an agreement for a definitive bilateral ceasefire and end to hostilities," the two sides said in a joint statement.

FARC commander Carlos Lozada tweeted: "On Thursday, June 23, we will announce the last day of the war."

The deal resolves one of the final points in peace talks between the Government and FARC, the country's biggest rebel group.

The deal is to be formally announced at a ceremony with Colombia's President Juan Manuel Santos and FARC commander Timoleon Jimenez.

The statement said foreign leaders and officials including UN Secretary-General Ban Ki-moon would attend.

Mr Santos said he hoped to seal a full peace deal by July 20.

"Tomorrow will be a great day!" he tweeted.

"We are working for a Colombia at peace, a dream that is starting to become a reality."

The accord covers "the laying-down of arms, security guarantees and the fight against the criminal organisations" accused of fuelling the conflict, the statement said.

'The UN is prepared to do whatever it can'

The means of implementation of a final peace deal remain to be settled.

Santos's Government wants a referendum to put the seal of popular approval on the peace.

The sides are discussing designating zones where the FARC's estimated 7,000 remaining fighters can gather for a UN-supervised demobilisation process.

"The UN is prepared to do whatever it can to strengthen the peace process," its deputy spokesman Farhan Haq said.

"We hope it will lead to a final agreement and the end of this long war."

The United States said its Special Envoy, Bernard Aronson, was heading to Havana to represent Washington at the ceremony.

The Colombian conflict, which started as a rural uprising in the 1960s, has drawn in various leftist rebel groups, right-wing paramilitaries and drug gangs over the decades.

The violence has left 260,000 people dead, 45,000 missing and nearly 7 million displaced, according to official figures.

Peace with the FARC would virtually end the conflict, but other armed groups are still operating.

AFP