Cuban leader Raul Castro took up the presidency of regional group Celac on Monday night in a demonstration of Caribbean and Latin American unity against US efforts to isolate his country through a 50-year economic embargo.
Mr Castro was warmly welcomed at the closing ceremony of the Celac summit in Santiago, taking over the rotating presidency from Chile.
He described "a common vision for the Latin American and Caribbean homeland," saying that Celac "joins the 33 independent nations of our America to build a space for national sovereignty and encourage integration."
Mr Castro said Venezuelan President Hugo Chavez had helped to realise Simon Bolivar's dream of unifying the region by negotiating the creation of Celac in December 2011.
Many of the leaders described it as a counterweight to the economic and political power of the US, which froze Cuba out of the Organisation of American States for decades.
"Cuba's assumption of the presidency marks a change of times," Argentinian President Cristina Fernandez said.
"For Chilean President Pinera to transfer the presidency to President Castro shows the times we're living in."
Uruguayan President Jose Mujica said it was refreshing to meet European leaders on equal terms for the first time in more than 70 years "without the boss from the north" at the table.
Venezuelan Vice-President Nicolas Maduro read a letter from Mr Chavez.
"After 30 years of resisting this criminal imperial blockade," Mr Chavez wrote, "Latin America and the Caribbean are using a single voice to tell the US: All your attempts to isolate Cuba are failing."