PORTO ALEGRE, Brazil, June 23 (Reuters) - By car, bus and plane, tens of thousands of Argentinians are crossing the border into southern Brazil in an invasion of the city of Porto Alegre for Argentina's match against Nigeria on Wednesday.
It promises to be a celebration of their shared "gaucho" culture as well as soccer. But police are also bracing for trouble from Argentina's notorious "barras bravas", hooligans who may try to spoil the party.
"In truth, this is very big for us," said Charles Muller, owner of stall in Port Alegre's public market selling soccer memorabilia.
"The Argentinians are welcome here. It will be like a gaucho fiesta. The hooligans are a minority who do not come for the football or the fun, just for trouble."
Brazil's southernmost state, Rio Grande do Sul, is indeed more akin to neighbouring Argentina and Uruguay than to the rest of the country.
They share the gaucho culture of the cowboys of the pampas, most visibly represented by the costume of baggy "bombacha" trousers, wide hats and big leather boots and belts.
People drink "mate" tea from gourds through metal straws and enjoy a good steak barbecue, just as across the border.
With a strong separatist tradition, many - Muller for one - identify themselves as Gaucho first and Brazilian second.
In the past, the region was fought over by the Spanish and Portuguese empires. After independence, Rio Grande do Sul was often in the frontline of wars between Brazil and Argentina and Uruguay - its people providing many of the soldiers.
Still, relations are good now, helped by the number of Argentinian tourists who flock to the state's beaches.
"We always have a lot of Argentines here, Uruguayans and Chileans too, not just during the World Cup. They come here for holidays," said Rosangela de Azevedo, manager of the Loja Casa do Gaucho shop in downtown Port Alegre.
"We are friendly rivals, particularly in football. They are not quiet."
She also expressed concern about the hooligans.
"Some of the fans are quite warlike. So we are scared about that. They are famously violent."
A spokeswoman for Rio Grande do Sul's public safety authority said 80,000 Argentines were expected in Porto Alegre for the game.
"We've been preparing ever since Porto Alegre was chosen as a host city. We are reinforcing security because of the sheer number of fans coming, not because they are Argentines," she told Reuters.
Special attention was being paid to the barras bravas, with precautions starting at the border. More police will be on the street and near the stadium. Police will escort buses filled with Argentine fans as they head to the stadium.
Many of the Argentinian fans do not have match tickets. Three of them - Maxmiliano Fornara, a 31-year-old professional, Mario Forti, 54, an engineer, and Franco Miseria, 27, doctor - were trying to score some spares on a rainy Monday morning.
They had arrived in town the previous night after a 14-hour, 1,300 km drive from Buenos Aires. They had managed to get a hotel room, even though accommodation is nearly packed out.
They said the hooligans were a minority and that the Argentinians were enjoying the brotherly atmosphere of Porto Alegre.
"The Argentine fans are the best in the world," Forti said.
Their team, spearheaded by forward Lionel Messi, is already assured of a spot in the last 16 even if their form has not yet approached the level expected of one of the pre-tournament favourites.
"Argentina will improve, Messi will improve and the others will follow. No one has the quality we have," said Fornara. (Additional reporting by Asher Levine in Sao Paulo, Editing by Nick Mulvenney)