Colombia and leftist FARC rebels said Sunday they have reached a deal on land reform, one of the most contentious items in negotiations aimed at ending five decades of insurgency.

The agreement between Bogota and the Revolutionary Armed Forces of Colombia would compensate those who have lost land or were displaced from their property, said Cuban diplomat Carlos Fernandez de Cossio, whose country played host to the months-long negotiations.

So far, the talks at the Havana Convention Center have focused almost entirely on land reform -- the first of five agenda items to be discussed.

Land distribution was one of the triggers of the protracted conflict in Colombia, where gaping inequality divides wealthy landowners and poor peasants.

The agreement on agrarian development "seeks to reverse the effects of the conflict and that the victims of forced displacement and looting obtain restitution," said Fernandez de Cossio, as he read a joint statement from the parties.

The step, the first major advance in six months of peace talks in Havana, was widely celebrated -- but it is part of a larger package still being bargained.

The joint statement warns that the advance on agrarian reform is "conditioned on reaching an agreement on the totality of the agenda," because the talks are based on the principle that "nothing is agreed upon until everything is agreed upon."

Chief government negotiator Humberto de la Calle, a former vice president, said in a statement to AFP that what the negotiators agreed upon "pertaining to the agricultural issue allows for a radical transformation of life in rural Colombia."

Colombian President Juan Manuel Santos gushed about the success in a message on his Twitter account.

"We sincerely celebrate this fundamental step in Havana towards a full agreement to put an end to half a century of conflict," Santos wrote.

"We will continue the peace process with prudence and responsibility."

The leftist leader of neighboring Venezuela, Nicolas Maduro, quickly congratulated the Santos administration and the rebel negotiators on the advances.

"It fills us with joy," he said during a visit to Bolivia.

Maduro's predecessor, the late Hugo Chavez, was friendly toward the FARC and supported the peace process.

In a Twitter message, Ecuador's foreign minister also congratulated both sides.

Both delegations will take a break of several days, and then begin talks on political participation, the second agenda point.

They are set to also discuss illicit drugs, decommissioning weapons and how to handle victims of the armed conflict.

The FARC, Colombia's largest guerrilla group with some 8,000 fighters, has been in talks with Bogota since November 19 to end their nearly 50-year-old insurgency, the longest-running in Latin America.

One of the rebel negotiators, Pablo Catatumbo, told the influential magazine Semana that Santos should be re-elected in the May 2014 presidential vote to guarantee that the peace process is fulfilled. The FARC rebels had earlier said they did not support the president's re-election.

Santos, 61, has been coy about his re-election plans. He does not need to decide until November.

Before becoming president in 2010, Santos was defense minister in the hard-line administration of his predecessor, Alvaro Uribe. In that post, he cracked down on the FARC and hunted down several rebel leaders.

Uribe, who remains popular, supported Santos's candidacy when he ran for office -- but the ex-president strongly opposes peace talks with the FARC, and now openly shows dissent with the president.

Santos took an enormous political risk in engaging the FARC in peace talks, but if the talks succeed he could easily win re-election, analysts say.