A land reform deal reached by Colombia's government and leftist FARC rebels marked a major step forward in their peace talks, but they still face a long slog to end Latin America's oldest conflict.

The land dispute was among the thorniest issues being negotiated between the administration of President Juan Manuel Santos and the Revolutionary Armed Forces of Colombia, whose rebellion began as a peasant insurrection in 1964.

After six months of negotiations in Cuba, which is facilitating the talks along with Norway, the two sides announced late Sunday a deal on "land access and use" and the "regularization of property."

Land distribution is an old and extreme source of tension in Colombia, where one percent of the population holds half of the rural land.

Santos released some details Monday night, saying the agreement would involve "comprehensive rural reform" based on four pillars.

He said these are distributing land to peasants who have none or not enough, via a "major land fund"; special development programs for areas most affected by the inequality; nationwide plans to improve health, education, housing and other services in rural areas; and food and nutritional security for rural people via greater food production.

The agreement won praise.

"It is a very important message for Colombians. Previous discussions with the FARC never went this far," Alejo Vargas, political expert at National University of Bogota, told AFP, stressing that the agrarian dispute was the "most complicated" issue of the conflict.

The government's three previous attempts at peace talks in the past 30 years never achieved such a result and ultimately failed. In 1984, the rivals managed to agree on a ceasefire, but it ended three years late after a wave of assassinations of elected officials close to the FARC.

Vargas said the land reform deal will create "some trust between the delegation" and has given the two sides a "way of working that works."

The fact that an agreement emerged on anything in the negotiations proves that communist Cuba was the right location for the talks, he said.

"It's been very useful. Cuba offers security guarantees and allows the delegations to work in peace. This wouldn't have been possible if journalists and cameras were present every day to ask about the progress," Vargas said.

The international community and the United Nations welcomed the agreement, while Santos described it as a "fundamental step" towards a full agreement to end a conflict that has left 600,000 people dead and 15,000 missing.

The handshake between government negotiator Franck Pearl and senior FARC member Pablo Catatumbo in Havana became a symbol of hope.

The rebel leader even made the surprising suggesting that he would favor Santos winning re-election next year in order to "give continuity to the peace process."

But the negotiations are taking place without a ceasefire and they still face many obstacles, including whether the rebels can avoid jail before returning to civilian life, the FARC's role in drug trafficking, disarmament and compensation for victims.

"We must be prudent and realistic because tougher questions that are even more divisive will come up," Javier Ciurlizza, regional director of the International Crisis Group, a non-governmental organization specialized in conflict resolution, told AFP.

"The path is still full of thorns and rocks," he said.

Implementing the land deal could prove tricky in the first place since legislation is needed to modify property rules.

"It's an enormous challenge because Colombia historically has had a deficit when it comes to agricultural property registries," Ciurlizza said.

The complex conflict once included far-right paramilitary militias that were created by wealthy landowners in the 1980s to combat the guerrillas and which officially demobilized in 2006.

Almost four million Colombians have been driven from their homes in the past five decades and the government has launched a plan to return two million hectares of land that was seized and another four million that was abandoned.

Ciurlizza said the redistribution of land will face "very important interests," while major investments will be needed to make it succeed.

"You need universal access to rural credit and techniques for these lands to be productive," he said. "This will require a lot of time and money."

The peace talks resume June 11. The next issues on the agenda include getting the rebels involved in politics, the drug trade, disarming the guerrillas and reparations to victims of the war.