The old enemies met in the last two finals of South America's top football tournament, with Brazil upsetting the favourites twice, but with home advantage at the July 1-24 event Argentina hope to win the trophy for the first time since 1993.
While Argentina have Messi, fast emerging as Diego Maradona's heir, at the heart of their attack, Brazil have their own brilliant player in Neymar, a potential new Pele who has already helped Santos win the Libertadores Cup at 19.
"It is our obligation to win the tournament," said Argentina coach Sergio Batista, who plays the high-scoring Messi in a roving centre forward role akin to his flexible position at Barcelona.
Argentina open the world's oldest active major soccer tournament at the modern, roofed Ciudad de La Plata stadium on Friday when they take on Bolivia in Group A.
They have a score to settle, having been thrashed 6-1 the last time they met in a World Cup qualifier at high altitude in La Paz two years ago during Maradona's time as coach.
Brazil, with coach Mano Menezes going back to the basics of his country's "beautiful game" after the pragmatic Dunga era, kick off against Venezuela in Group B at the same venue on Sunday before heading for Cordoba to play Paraguay and Ecuador.
Menezes' pair of aces are Neymar and his 21-year-old Santos team mate Paulo Henrique Ganso, an exquisite playmaker the coach hopes will spark Robinho, a veteran of Brazil's 2007 victory, and Alexandre Pato up front.
"There is a very strong [team] base around Diego Forlan [and] he is in very good physical condition [after a refreshing break]," said coach Oscar Tabarez, one of the few coaches to survive a post-World Cup cull.
"I think Colombia will have a good Copa America, a good World Cup qualifying campaign and qualify for the finals [in Brazil in 2014]," Pa
