Argentina remain on course to retain their Olympic soccer crown after a 3-0 semi-final win over South American rivals Brazil in a bad-tempered clash.
Brazil ended the game with nine men after two late red cards, including one for midfielder Lucas for a lunge on his Liverpool team-mate Javier Mascherano nine minutes from the end.
Lucas was followed for an early bath by Thiago Neves for another foul on Mascherano three minutes later as Brazil's gold medal hopes evaporated at Beijing's Workers' Stadium.
Sergio Aguero opened the scoring when he chested home Angel Di Maria's cross with 52 minutes on the clock after a sedate first half.
Rafael Sobis then hit the post for Brazil but Aguero doubled the score when he touched in Ezequiel Garay's low cross.
Ronaldinho thumped the post with a free-kick before Alexandre Pato had a goal ruled out.
And Juan Roman Riquelme made it three with a penalty 14 minutes from the end before Brazil's discipline completely deserted them with the two late red cards.
Argentina will now meet Nigeria in a repeat of the 1996 final after the African side tore apart Belgium to win 4-1.
Olubayo Adefemi opened the scoring with a low drive after 16 minutes which Logan Bailly was unable to keep out.
Victor Anichebe set up Chinedu Ogbuke Obasi for the second just before the hour mark, and Obasi added his second in style 18 minutes from the end with a long-range effort.
And Chibuzor Okonkwo made it 4-0 with another long-range strike six minutes later, before Laurent Ciman's late consolation.
The Nigerians will now be hoping to repeat their famous win of 1996, when goals from Celestine Babayaro, Daniel Amokachi and Emmanuel Amunike secured a 3-2 triumph.
