Between March 19 and 23, US President Barack Obama will travel to Brazil, Chile and El Salvador "to forge new alliances across the Americas." Background on U.S. and Brazil's economic ties:
Brazil, for its part, has recently announced its foreign policy aims under new President Dilma Rousseff, saying it would continue the dialogue with Iran, "because isolation sometimes only exacerbates a worrying situation that could lead to a conflict". 
Ever since Mahmoud Ahmadinejad’s election as Iran's president in 2005, ties between the Islamic Republic and several Latin American states have been growing stronger, posing new challenges to the US.
Over the past few years, US security officials have expressed concerns over Iran's attempts to undermine US international influence and its terrorist and drug-related activities in Latin America. Read more at Realite
The United States and Brazil, the two largest economies and the two largest democracies in the Western Hemisphere, share one of the most important trade and economic relationships in the world. Brazil is our 10th largest trading partner. U.S. goods and services exports to Brazil in 2010 are estimated to be more than $50 billion, which will support more than 250,000 jobs. U.S. goods and services exports to Brazil are growing twice as fast as overall U.S. goods and services exports.Background on U.S. and Central and South America's economic ties:
Brazil is an emerging global player and economic powerhouse. With a 2010 GDP of more than $2 trillion, Brazil is the 7th largest economy in the world and accounts for nearly 60 percent of South America’s total GDP. Brazil’s economy grew by 7.5 percent in 2010 and is anticipated to grow by between 4 and 5 percent in 2011.
As the U.S.-Brazil relationship deepens, we seek to base our cooperation on strong and dynamic private sectors, a commitment to open and fair trade, and continued economic and energy integration. Strengthening the economic and commercial relationship between the U.S. and Brazil through stronger partnerships on energy (including clean energy, biofuels, and petroleum sectors), infrastructure and development cooperation in third countries will allow both countries to grow and at the same time strengthen the bonds between the U.S. and Latin America. Read more from the White House background sheet
President Obama is committed to enhancing U.S. leadership in Central and South America, and at the same time, recognizing the region’s emerging markets as key players in the global economy. Central and South America’s rapid pace of growth – around 6 percent in 2010 – is creating new opportunities for mutually beneficial trade that creates prosperity abroad and new jobs at home. We are connected to Central and South America not just by a common geography, but by common interests and values.
The President set a goal of doubling our exports by the end of 2014, and with nearly 20 percent growth since 2009, we are on pace to meet this challenge. But as the United States competes globally, strengthening our partnerships for progress with our American neighbors is crucial to winning the future. U.S. trade agreements with Central and South America already cover 7 countries and $471 billion in total goods trade with more set to be added when the outstanding issues with Panama and Colombia are resolved and those FTA’s are put forward for Congressional approval. These agreements, along with extensive trading and investment relationships and government-to-government mechanisms to promote United States economic engagement in the region are positioning the U.S. to successfully compete in Central and South America and around the world.
United States trade facilitation and technical assistance partnerships with Central and South American countries has helped to strengthen economic institutions across the region and further integrate countries into the global trading system and improved economic linkages to the United States. Read more at the White House background sheet