Defending champions United States will get a second chance to make the women's Olympic 4x100m relay final.

They dropped the baton in the heats but were obstructed and must now beat the time set by eighth-fastest China when they run again at 00:00 BST.

Britain's women finished second (41.93 seconds) behind fastest qualifiers Jamaica (41.79) to progress.

The US men qualified fastest (37.65) with Jamaica, without Usain Bolt for the heat, fifth fastest and GB seventh.

Jump media playerMedia player helpOut of media player. Press enter to return or tab to continue.

A mix-up between Allyson Felix and English Gardner on the second changeover saw the US women out of contention in the second heat before they were given a second chance on appeal.

"I think I got propelled at about 20 miles an hour," said Felix. "When a foreign object comes in front of you, it's going to mess up the momentum and the handover."

There was another shock in the women's event as Dafne Schippers made a changeover error, leading to the Dutch - European champions - going out in the heat.