Santiago: It`s a geopolitical rivalry that has seen a clash of generals, a near-war over territory, and accusations of treachery and arrogance.
Now it`s getting serious. Argentina and Chile are playing a soccer final.
On Saturday, the two South American neighbors will battle it out to be crowned champions of the quadrennial Copa America, a tournament followed with a fervor on the continent that comes second only to the World Cup. And perhaps none want to win it quite so badly as Chile and Argentina.
For Chile - playing as hosts - it would be the first time they lift the trophy. Argentina have a more impressive record but despite reaching last year`s World Cup final have not won major silverware in 22 years.
The Copa has been largely good-natured, with little of the fan violence that often mars regional matches. Fans have respected a campaign discouraging jeering during others` anthems.
But now Chile are meeting Argentina in the final, and there are signs the detente is beginning to crack.
Animosity dates back to the 1970s, when both countries were led by military juntas, and nearly came to blows over a border dispute. Then in 1982 when Argentina fought a war with Britain over the Falklands/Malvinas islands, Chile backed the European power.
Argentina has not forgot, nor forgiven.
Ex-Argentine soccer star Diego Maradona said in a TV interview just last month that the Chileans "sold us out in the Malvinas".
Argentine fans taunt the hosts as `traitors` in their chants, including the harshly worded song: "although the years pass we will never forget because you`re a traitor...hopefully the sea will cover you, let the English help you swim."
In Concepcion, which in 2010 was hit by a devastating tsunami, those words did not go down well, and at Tuesday night`s semi-final in the city Argentina`s anthem faced boos and whistles by Chilean fans in the stands.
Locals on the streets of Santiago and Buenos Aires said playing against each other was about more than just soccer.
"I think there`s something psychologically unique about going up against Argentina because we are neighbors, and despite that we have very different personalities. So, it`s like standing up to the big, bad guy next door," said Chilean shopkeeper Carmen Gloria.
Wary of a violent reaction after Saturday`s results - Chilean fans often go on a rampage after a big soccer win or loss, while Argentine `barra brava` hooligans are among the continent`s most notorious - the police have increased their planned presence at the final.
Politicians and players have appealed for calm.
"I hope the people understand that football is a sport...there is no war here," said Argentine midfielder Javier Mascherano after Tuesday`s match.
"We are sister countries and we have to respect each other."