Both players displayed their uncanny skills, but Messi threatened the most and created dangerous scoring chances for Argentina. In his first Olympics, the midfielder set up Argentina's second and third goals, while AC Milan's Ronaldinho struck the post with a free kick as he tried to put Brazil back into the match.

Ronaldinho (L) of Brazil challenges Fernando Gago of Argentina for the ball during the 2008 Beijing Olympic Games men's football semifinal match in Beijing on August 19, 2008.[Agencies]

Messi sent a dangerous shot across the area in the 32nd, and had one of his best chances in the 41st after clearing three defenders inside the area before firing a shot that was barely saved by goalkeeper Renan.

Aguero ran past defender Breno to open the scoring after Angel di Maria's cross, then easily added to the lead in front of the goal mouth after Ezequiel Garay's set-up. Messi started the play on the second goal by eluding several defenders before feeding the ball to Garay.

Messi also set up Aguero inside the area before he was fouled by Breno in the play that prompted the penalty kick, which Riquelme converted with a right-footed shot into the middle of the net.

After Aguero's first goal, striker Rafael Sobis almost equalized with a powerful low shot that struck the post in the 60th. Ronaldinho also hit the post on a free kick in the 65th. Substitute forward Alexandre Pato scored after the free kick, but the goal was disallowed for offside.

"We played an even match with them, it was a hard game, as usual," Brazil coach Dunga said. "But they got the first goal and that made things difficult."

Brazil midfielder Lucas was sent off in the 81st after a foul from behind on Liverpool teammate Javier Mascherano. Substitute midfielder Thiago Neves was red-carded just three minutes later after another hard foul on Mascherano.

"It was Argentina's best match in the Olympics so far," Batista said. "It was a well-deserved result."

Players from Argentina celebrate after defeating Brazil during the 2008 Beijing Olympic Games men's football semifinal match in Beijing on August 19, 2008. Argentina beat Brazil 3-0 to qualify for the final. [Agencies]

The teams had drawn 0-0 in World Cup qualifying earlier in June, but Brazil routed Argentina 3-0 in last year's Copa America and won by the same score in a friendly in London in 2006.

"Now we will try to win the bronze," Pato said. "It will still be an honor to win that medal."

In the other semifinal, Nigeria beat Belgium 4-1 in Shanghai after Chinedu Ogbuke Obasi scored two goals and Olubayo Adefemi and Chibuzor Okonkwo added one each for the 1996 Olympic champions.