Argentina's President Cristina Fernandez de Kirchner (Back) greets her Brazilian counterpart Dilma Rousseff (Front) prior to their meeting at Government Palace in Buenos Aires, capital of Argentina, on April 25, 2013. (Xinhua/Martin Zabala)

Argentina's President Cristina Fernandez de Kirchner (R) greets her Brazilian counterpart Dilma Rousseff prior to their meeting at Government Palace in Buenos Aires, capital of Argentina, on April 25, 2013. (Xinhua/Martin Zabala)

Brazilian President Dilma Rousseff (L) talks to journalists with her Argentine counterpart Cristina Fernandez de Kirchner after a working meeting at Government Palace in Buenos Aires, capital of Argentina, on April 25, 2013. (Xinhua/Martin Zabala)

Argentina's President Cristina Fernandez de Kirchner talks to journalists after a working meeting with her Brazilian counterpart Dilma Rousseff (unseen) at Government Palace in Buenos Aires, capital of Argentina, on April 25, 2013. (Xinhua/Martin Zabala)

Brazilian President Dilma Rousseff (L) talks to journalists with her Argentine counterpart Cristina Fernandez de Kirchner after a working meeting at Government Palace in Buenos Aires, capital of Argentina, on April 25, 2013. (Xinhua/Martin Zabala)

Argentina's President Cristina Fernandez de Kirchner (R) talks with her Brazilian counterpart Dilma Rousseff prior to their meeting at Government Palace in Buenos Aires, capital of Argentina, on April 25, 2013. (Xinhua/Martin Zabala)

Brazilian President Dilma Rousseff talks to journalists after a working meeting with her Argentine counterpart Cristina Fernandez de Kirchner (unseen) at Government Palace in Buenos Aires, capital of Argentina, on April 25, 2013. (Xinhua/Martin Zabala)