WATCH: US relay team given second chance to qualify after obstructed baton exchange

They were one of the race favourites.

Update 4.55pm: The US team will be allowed to run on their own in the evening session and try to qualify on time.

The IAAF Jury of Appeal decision was that they were obstructed at the second exchange.

The US will have to run faster than China's 42.70 from the heats to book a place in the final.

Earlier:The US women’s 4x100m relay team, who were among the medal favourites, have failed to qualify for the finals.

They were eliminated after Allyson Felix and Tianna Bartoletta made a mess of their baton exchange.

Germany, Nigeria and Trinidad and Tobago took the first three places and go forward to the final.

There are unconfirmed reports online that the US have launched an appeal - claiming that Felix was bumped by another athlete immediately prior to the changeover.