SIMON Yates' lead in the race for the white jersey at this year's Tour de France was cut by 90 seconds in a punishing penultimate mountain stage.

South African rival Louis Meintjes moved to within 2mins 28secs of the Bury cyclist, who is bidding to follow his twin brother Adam's feat of last year and become only the second Brit to win the tour's prize as the best young rider.

At the head of the race, Chris Froome extended his lead in the yellow jersey as former ski jumper Primoz Roglic sailed over the Tour de France's highest mountain to win stage 17 into Serre-Chevalier.

Roglic went solo six kilometres from the top of the Col du Galibier and crested the summit with a 90-second lead before racing down the 28 kilometre descent to the finish.

Most of the main contenders were in the second group on the road, 73 seconds further back.

Colombian Rigoberto Uran took second place for six bonus seconds while Froome pipped French rival Romain Bardet to the line for the final four.

That sees three-time Tour winner Froome extend his lead, with Uran and Bardet both now 27 seconds back.

Italian national champion Fabio Aru had been dropped on the Galibier and conceded more than 30 seconds to lose his grip on second place overall.

Aru dropped down to fourth, 53 seconds off yellow. Froome's team-mate Landa sits fifth while Irishman Dan Martin moved up one place to sixth, pushing Yates back into seventh, with a battling performance 24 hours after he was caught out in crosswinds and gave up two spots in the general classification.

For Team Sky's Froome it was a case of job done as he ticked off the first of two Alpine stages which could decide this year's Tour even before Saturday's time trial in Marseille.

"I didn't have the legs in the Pyrenees," said Froome, who had lost yellow on stage 12 to Peyragudes before reclaiming it 48 hours later.

"But now I feel strong. I've also got to look towards tomorrow because it's a summit finish on Izoard and I'll have to see how the legs are."

The main rivals had all tested each other on the long gradual climb of the famed Galibier, the highest point on this year's Tour with a summit at 2,642m, but they could only shake off Aru.

For only the second time in the Tour, Yates was dropped by the leaders, but he gathered all his reserves of energy to struggle back, finishing 3:14 seconds behind Roglic.

"I think I did well to limit my losses really," Yates said. "I rode full gas. I wasn't strong enough, there was quite a lot of wind about and I got tailed off towards the end.

"I really fought hard to stay on because I knew it was a long way to the finish, but I couldn't do anymore."