Those attending included Venezuelan President Nicolas Maduro and Brazilian President Dilma Rousseff. The leaders of Chile, Argentina, Uruguay and Colombia sent delegations to represent them.
The summit was held hours after the son of Suriname President Desi Bouterse was arrested Thursday in Panama on U.S. drug and weapon charges. Dino Bouterse pleaded not guilty in a New York federal court on Friday.
Desi Bouterse, himself previously convicted of drug offenses, did not talk about the arrest after delivering his welcoming remarks.
Mike Antonius, Suriname's UNASUR diplomatic representative, said officials were not talking about the case.
"We were busy with UNASUR matters and were somewhat unaware of what was happening in the outside world," he said.
The summit marked the transfer of UNASUR's rotating presidency from Peru to Suriname, the smallest country in South America.
UNASUR was created in May 2008 after 12 South American countries signed a treaty to advance the region's interests, including the creation of a single market.
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Associated Press Writer Pedro Servin in Asuncion, Paraguay contributed to this report.