Allyson Felix took the final women's 100-metre spot on the US Olympic squad, after her rival Jeneba Tarmoh pulled out of their scheduled run-off.

The 26-year-old Felix ran a dead heat for third place with Tarmoh at the United States Olympic trials on June 24.

USA Track and Field asked the pair to race again yesterday to decide the final sprint spot.

However, Tarmoh wrote to USA Track and Field president and chairman Stephanie Hightower announcing that she was standing down.

With a time of 11.07 seconds, both Felix and Tarmoh are some way behind current Olympic champion Jamaica’s Shelly-Ann Fraser-Pryce, who recorded 10.70 seconds at the Jamaican Olympic trials.

Fraser-Pryce ran 10.78 seconds to win Olympic 100-metre gold at the 2008 Olympics in Beijing, 0.14 seconds faster than Felix's personal best.