BERGERAC, France?- Riders are setting off one-by-one in the Tour de France's Stage 20 time trial, with two places on the final podium beneath yellow-jersey holder Vincenzo Nibali up for grabs.

Last-placed Ji Cheng of China was first off on the 54-kilometer (34-mile) rolling route from Bergerac to Perigeuex as riders set off in reverse order of the overall standings.

Italy's Nibali has a near lock on victory, leading by more than 7 minutes over second place Thibaut Pinot of France.

Three-time world time-trial champion Tony Martin of Germany is the favorite to win the stage.

Only 15 seconds separate Pinot and the third- and fourth-placed riders Jean-Christophe Peraud and Alejandro Valverde.