Union of South American Nations in Mitad del Mundo, Ecuador, where the cornerstone was laid for the headquarters of the General Secretariat of the Union. In April 2018, six countries suspended membership: Argentina, Brazil, Chile, Colombia, Paraguay and Peru. In August 2018, Colombia announced its withdrawal from the organization. At the Third South American Summit on 8 December 2004, presidents or representatives from 12 South American nations signed the "Cusco Declaration", a two-page statement of intent announcing the foundation of the South American Community. Panama and Mexico attended the signing ceremony as observers in Brazil. The mechanics of the new entity came out of the
Union of South American Nations and Argentina are considered the regional leaders of South America. They are the two largest nations and the two largest economies in South America. These are the only South American countries that are members of the G-20 and Brazil, specially, as member of the BRICS. They're also the largest producers and exporters of agricultural products of the continent. The highest nominal GDP in 2017 is Brazil (8th worldwide) with 2,140,940 trillion dollars, followed by Argentina (21st worldwide) with 628,935 billion dollars, and Colombia (31st at the global level) with 306,439 billion dollars. The highest GDP in 2017 is in Brazil