By Julien Pretot
CHORGES, France (Reuters) - Chris Froome continued his march towards a maiden Tour de France title when he beat fierce rival Alberto Contador by nine seconds to win the 17th stage, a 32-km time trial on Wednesday.
Team Sky rider Froome, who has now three stage wins to his name in the Tour this year, clocked 51 minutes 33 seconds to extend his overall lead over second-placed Contador to 4:34 going into three grueling stages in the Alps.
"It's a surprise for me to win today," Briton Froome told reporters.
"The first descent was dangerous and technical, I did not want to take risks.
"I was a bit down in the first two time checks but I feel the bike change helped me towards the end," added Froome, who switched to a time trial bike just before the second time check.
Spain's Joaquim Rodriguez took third place on the day one second behind Contador as Dutchman Bauke Mollema lost his third place overall to Czech Roman Kreuziger, who trails Froome by 4:51.
The time trial featured two second-category climbs and two descents, the first one being particularly tricky.
Contador went full throttle after opening a two-second gap on the first time check but Froome, who on Tuesday accused the Spaniard of careless riding, had more in the tank.
France's Jean-Christophe Peraud, ninth overall before the start of the stage, had a nightmarish day. He broke his right collarbone in a crash during a training ride but decided to take the start, only to come off his bike again two kilometers from the finish.
Unsurprisingly, Peraud pulled out of the race.
Thursday's 18th stage takes the peloton from Gap to l'Alpe d'Huez, with the 21 hairpins to the resort being climbed twice with the treacherous descent from the Col de Sarenne sandwiched in between.
Up to one million spectators are expected on the ascent, according to the local office of tourism quoted by French TV.
(Editing By Alison Wildey)