LONDON (Reuters) - Dutch rider Tom Dumoulin is still hopeful of competing for road time trial gold at the Rio Olympics despite breaking his left arm near the end of the Tour de France.

Dumoulin, regarded as the biggest threat to Chris Froome for the time trial on the hilly Grumari circuit on Aug. 10, posted a video on Twitter of him back on his bike.

"Look what I'm doing?" Dumoulin who won stage nine and 13 on the Tour but suffered a heavy fall on stage 19, said as he filmed himself out pedaling on the road.

"It's a bit stiff but it's okay. At least I can ride my bike. Don't try this at home!"

The 25-year-old faces a race against time to be fit for Rio, although the break to his forearm was clean and there was not thought to be any damage to the wrist.

(Reporting by Martyn Herman, editing by Pritha Sarkar)