Mercado ComÃºn del Sur (Southern Common Market). A South American trade bloc that aims to promote free trade and cooperation between its members. Argentina, Brazil, Paraguay and Uruguay are full members as of 2008. Venezuela is a full member pending ratification. Chile, Bolivia Colombia, Ecuador and Peru are associate members. The headquarters are in Montevideo, Uruguay. A Mercosur parliament was inaugurated in December 2006 and began meeting in May 2007.