By Stephen Gibbs
BBC News, Havana
Venezuelan President Hugo Chavez is in Cuba on a visit designed to strengthen links between the economies of the two leftist countries.
Chavez (l) and Castro were buoyant
Venezuela already provides Cuba with half the oil it requires at highly preferential rates.
President Chavez has said that he hopes to expand trade with Cuba to around $1bn a year.
The alliance is designed to be a rival to the US proposal for the Americas to become a single free trade area.
Washington's two least favourite Latin American leaders appeared in jovial mood together as they opened a new office for Venezuela's state petroleum company in Havana.
The US government has accused Mr Chavez of pursuing an authoritarian form of government.
A smiling President Chavez in a bright red shirt frequently had his arm around Cuban President Fidel Castro, who was wearing his traditional military fatigues.
Both leaders have indicated that they want to expand their bilateral trade dramatically.
Already Venezuela provides an economic lifeline to Cuba's struggling economy.
Cuba receives 53,000 barrels of Venezuelan oil a day at almost half the current market rate.
It pays partly in kind, by loaning Venezuela educational and medical services, most notably several thousand doctors.
It is this trade model that the two presidents want to expand across the region as a radical alternative to the US-backed Free Trade Area of the Americas.