The standard-bearers of Colombia's main leftist parties, the Alternative Democratic Pole and Union Patriotica, on Friday registered their candidacies for president and vice president on a unity ticket.

The Pole's Clara Lopez and Aida Avella of UP made the alliance official a day after their respective parties agreed to join forces.

"Great efforts have been made for unity, we have spent many hours talking, but today we can say that we begin another chapter of the history of that unity of the left needed to tell this country that we have another conception of the direction of the state," Avella said.

Lopez and Avella registered their individual presidential candidacies last week, but left the door open to a merged ticket.

"This is a ticket ... of two fighting women who - I must say - have suffered much persecution, the pain of loss, of victimization, of the political intolerance of this country, but we are turning the page," Lopez said.

Avella and Lopez were originally colleagues in Union Patriotica, which was born in 1985 of a pact between the government and the FARC rebel group that was intended to bring the rebels into the democratic process.

Within a decade, however, some 4,000 UP members were slain by right-wing paramilitaries and the security forces.

Avella, then the UP leader, went into exile in Switzerland in 1996 after surviving a paramilitary attack.

The main points of the left alliance platform include support for current President Juan Manuel Santos' peace talks with the FARC and calls for a new economic model that favors family farmers over agribusiness and promotes domestic industry instead of pursuing free-trade deals.

Santos goes into the May 25 election heavily favored to win a second four-year term. EFE