Jamaica's bid for the men's 4x400 metres relay gold was cut short by injury today when Jermaine Gonzales pulled up with an injury in the third leg of their heat.
The world championship bronze medallists, who had fancied their chances of ending America's dominance in the event, looked devastated with Gonzales on his knees in despair.
Usain Bolt, the world's fastest man, had said today there was a slim chance he might have run in the final for Jamaica.
The heat was won by Beijing silver medallists the Bahamas with a season's best of 2 minutes 58.87 seconds, nipping just in front of world champions and winners of the event at the last seven Olympics, the United States.
Joining them in Friday's final will be medal contenders Trinidad and Tobago and Britain, who finished first and second in the day's first heat.
South Africa's double-amputee Oscar Pistorius's much anticipated run never materialised after his compatriot Ofentse Mogawane collided with Kenya's Vincent Mumo Kiilu on the last bend of the second leg and was too hurt to continue.
Pistorius, who races wearing carbon fibre prosthetic blades after being born without a fibula in both legs, stood with his hands on his head but stayed to clap his race rivals home.