Unasur includes members of other regional groupings, notably the Mercosur trade bloc and the Andean Community of Nations. In recent months it has sought to exert influence on the defense spending of countries on its Defense Council, which is meeting in the Peruvian capital this week.
Defense ministers were in discussions to work out an action plan for 2012 that would include comparing military expenditures of member countries.
Besides host Peru the Defense Council comprises Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Suriname, Uruguay, Venezuela and Paraguay, the current chair of the body.
Unasur picked up on regional diplomatic initiatives that followed an outcry over defense spending critics saw as disproportionate to the needs and called on governments to invest instead in economic development and poverty reduction programs.
Most of the increased defense spending in Latin America and neighboring countries has less to do with political tensions and more rooted in the governments' eagerness to upgrade military infrastructures neglected due to scarce cash. Even the larger nations, including Argentina, Brazil and Chile, used recent commodities trade surpluses to modernize their armed forces, incurring large allocations for defense as a result.
But defense spending also saw a spike due to the rising tensions between Colombia and Venezuela over a military cooperation accord between Bogota and Washington. Venezuela interpreted the deal as a threat to its own security. Colombia accused Venezuela of aiding guerrillas seeking to overthrow its administration.
Unasur stepped in with a diplomatic initiative that eased the stand-off between Colombia and Venezuela -- Unasur's crowning achievement so far. Analysts said the reconciliation between pro-West Colombia and anti-West Venezuela had also much to do with change of political climate after President Juan Manuel Santos assumed power in Bogota August 2010 and Venezuelan President Hugo Chavez sought a way out of a dangerous impasse. In later months, Chavez mellowed toward Colombia as concern over his health and treatment for cancer kept him preoccupied.
The proposed action plan 2012 is seen by analysts as an acid test for Unasur, as it requires member countries to provide information on defense acquisitions, overall military spending and security issues. The data will be pooled under Paraguay's supervision and analyzed for accuracy and inconsistency.
It isn't clear how Unasur will deal with violations as they surface during the planned scrutiny.
Unasur is aiming to turn its membership area into a single market, modeled after the European Union, but troubles in Europe have made many officials skeptical about that goal.
Unasur has administrative headquarters in Quito, Ecuador, covers an area of 6,846,154 square miles and has a population of 400 million.
Unasur members are Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana, Paraguay, Peru, Suriname, Uruguay and Venezuela. Mexico and Panama are observers.