Cuban leader Fidel Castro hosted Venezuelan President Hugo Chavez and Bolivian President Evo Morales in a show of unity for the strongest critics of the United States in Latin America.
Bolivia joined Cuba and Venezuela in the Bolivarian Alternative for the Americas (ALBA), an initiative promoted by Castro and Chavez in an attempt to thwart US plans for the Free Trade Area of the Americas (FTAA).
"ALBA is moving forward, and facing the aggression of the imperial projects of the free trade agreement," Chavez said.
Castro added: "The best defence is to counter-attack and this is what we have done."
The trio also signed a "People's Trade Treaty" in which oil-rich Venezuela will boost crude and gas exports to Bolivia.
"Now, for the first time, there are three of us," said Castro, who heads the Americas' only one-party Communist state. "I believe that, one day, all (Latin American) countries can be here."
Morales said the treaty will help Bolivia emerge from an economic crisis."
"Only in Cuba and Venezuela can we get unconditional support," he said.
Chavez, who has become a thorn in Washington's side since his 1998 election, praised what he described as Cuba's economic achievements under the leadership of Castro, his key regional ally.