Argentina crushed Brazil in one of football's most combustible rivalries today to reach the Olympic final where they will play African giants Nigeria who sauntered past minnows Belgium.
The defending champions, inspired by Barcelona superstar Lionel Messi who outshone AC Milan's Ronaldinho, upset their South American neighbours with a brace from Sergio Aguero and penalty by captain Juan Riquelme.
It means that Brazil, despite being five-time World Cup winners, must wait another four years for a chance to win their first Olympic gold after coming up short twice before in final appearances in 1984 and 1988.
Atletico Madrid's Aguero broke the deadlock seven minutes after the interval when Angel Di Maria's pass appeared to strike his upper arm and flew into the net.
Aguero scored his second five minutes later when Messi released defender Pablo Zabaleta on the right and his pass was slotted home from close range.
Riquelme killed off the game with a 76th minute penalty after Aguero was brought down by Bayern Munich defender Breno.
It was wretched night for the Brazilians with Liverpool midfielder Lucas and substitute Thiago Neves both sent off for ugly fouls on Javier Mascherano late in the second half.
In Shanghai, 1996 Atlanta Olympic champions Nigeria proved too big a hurdle for Belgium, comfortably winning 4-1.
Olubayo Adefemi opened the scoring in the 17th minute and Chinedu Ogbuke Obasi netted a brace before Chibuzor Okonkwo hammered the final nail in Belgium's coffin.
Substitute Laurent Ciman pulled one back in the dying minutes but it was too little too late.
"It was unbelievable. You just have to look at the scoreboard," said Nigeria's ecstatic coach Samson Siasia. "We are going for gold."
Nigeria came out firing on all cylinders with Belgian goalkeeper Logan Bailly called into action twice in the opening minute, parrying a tricky cross then getting down low to save a shot from captain Victor Obinna.
The Nigerians, with the inherited experience of six Olympics, pressed the attack and a sustained period of pressure resulted in the opener.
The Belgian defence was at fault, failing to clear the ball and it fell to Adefemi inside the box and he slotted it underneath the diving Bailly.
Hertha Berlin forward Solomon Okoronkwo almost made it 2-0 ten minutes before the break when his pace took him past a defender but his drive whistled past the post.
At the other end, Ajax midfielder Jan Vertonghen struck a beautiful volley after connecting perfectly with a lofted corner kick, only to see Nigerian keeper Ambruse Vanzekin somehow keep it out.
The Africans got the all-important second goal after 59 minutes, but they were fortunate as Ogbuke Obasi looked to be offside when Everton's Victor Anichebe fed him the ball.
He put it in the net with the outside of his left boot and Chilean referee Pablo Pozo allowed it to stand.
The match was put beyond doubt with 18 minutes remaining when Obinna laid off the ball to a rampaging Ogbuke Obasi who hit a powerful strike from 25 yards that gave Bailly no chance.
A long-range effort from Okonkwo in the 78th minute added to Belgium's misery.
"We deserved it," said Odemwingie. "We have the confidence to win a gold medal for Africa."
