The 66th Mercosur summit in Buenos Aires ended with Argentine President Javier Milei formally transferring the bloc’s rotating six-month presidency to Brazil’s Luiz Inácio Lula da Silva. In his valedictory address, Milei urged a sweeping reduction of trade barriers, called the customs union a "cortina de ferro" that hinders competitiveness, and warned that Argentina could abandon the group if it fails to liberalise. He also demanded the "immediate" release of all political prisoners in Venezuela, including detained Argentine gendarme Nahuel Gallo. Lula, taking charge of Mercosur for the sixth time, countered that the common external tariff shields members from global trade wars and said "estar no Mercosul nos protege". He pledged to press for ratification of the long-delayed Mercosur-European Union trade agreement before year-end, advance regional climate and energy-transition policies and study Milei’s proposal for an agency to fight transnational crime. On the sidelines, Lula met Paraguayan President Santiago Peña. The pair agreed to restart negotiations on Annex C of the Itaipu hydroelectric treaty—frozen since allegations that Brazil’s intelligence agency Abin spied on Paraguayan officials—and to improve cross-border infrastructure. According to a Brazilian government statement cited by Reuters, Lula accepted Peña’s invitation to visit Asunción. The Brazilian leader also held brief talks with Uruguayan, Bolivian and Panamanian delegations and said Brasília would support exploratory negotiations for a Mercosur-Panama accord, underscoring a push to widen the bloc’s external agenda. After the summit, Lula visited former Argentine president Cristina Kirchner at her Buenos Aires residence, declaring “acredito na inocência de Cristina” despite her corruption conviction. The gesture drew criticism from Argentine and Brazilian opposition figures, adding domestic political friction to an already contentious regional gathering.