The Australian men's 4x400 metres relay team has missed a spot in the final after incident-packed heats at the Olympic Stadium.
Individual 400m finalist Steve Solomon started the race and ran the fastest first leg of the race (45.6) to hand over to Ben Offereins.
He ran the first half of his lap boldly but weakened (46.3) and the Australians were last at the second baton change.
Brendan Cole (45.48) then handed over to John Steffensen in fifth, but he was unable to make up any ground and finished in 45.67.
Australia was sixth over the line in 3:03.17, but initial disqualifications to the Dominican Republic and Venezuela saw them promoted to fourth, one spot outside the three to automatically qualify.
But Venezuela were later reinstated, while Jamaica failed to finish after one of its runners pulled up with a leg injury.
The Jamaicans had fancied their chances of ending America's dominance in the event, with Usain Bolt, the world's fastest man, even suggesting there was a slim chance he might have run in the final.
The Bahamas and the US advanced when both posted the time of 2:58.87, but the passage of the Americans was not as painless as it had first appeared after Manteo Mitchell revealed he broke his leg half way round the track but still managed to finish.
The 25-year-old ran the first leg and although he finished with a limp there was no obvious sign of the pain he was feeling.
"I got out pretty slow, but I picked it up and when I got to the 100-metre mark it felt weird," he said.
"As soon as I took the first step past the 200-metre mark, I felt it break. I heard it. I even put out a little war cry, but the crowd was so loud you couldn't hear it.
"I knew if I finished strong we could still get it [the baton] around. I saw Josh Mance motioning me in for me to hand it off to him, which lifted me. I didn't want to let those three guys down, or the team down, so I just ran on it. It hurt so bad."
Mitchell, who ran his leg in 46.1, says he slipped on a stairway this week in the Olympic village but had completed work-outs since, including a warm-up for Thursday's race.
After the race an X-ray revealed he had broken his left fibula bone.
The US was already without 2008 Olympic 400m champion LaShawn Merritt, whose title defence lasted only moments last Saturday when he pulled up with hamstring problems.
The US, one of the favourites for gold, will name its final line-up on Friday.
There was also action in the first heat, which saw a collision between Vincent Mumo Kiilu of Kenya and South African runner Ofentse Mogawane.
Mogawane crashed to the ground and dislocated his left shoulder, leaving his double amputee team-mate Oscar Pistorius stranded at the start-finish line.
While Kiilu picked himself up and continued on, the Kenyans were later disqualified "as their runner had cut across and caused the South African runner to fall", the IAAF said in a statement.
South Africa was advanced to the now nine-team final by the jury of appeal even though they did not finish the race.
Host nation Britain produced an impressive run in the first of two heats, with anchor Martyn Rooney easing up on the line to allow Trinidad and Tobago to pip them in a national record of 3:00.38 - both teams progressing with the same time.