Bradley Wiggins moved within three days of becoming the first British winner of the Tour de France after successfully negotiating the final day in the Pyrenees and putting further time on his rivals for glory.
Wiggins began the 143.5-kilometre route from Bagneres-de-Luchon to Peyragudes in the yellow jersey for a 10th day and with a lead of two minutes five seconds over Team Sky colleague Chris Froome, with Italian Vincenzo Nibali (Liquigas-Cannondale) 18 seconds further adrift.
No other rider was within five minutes of the triple Olympic champion and Nibali knew he had to make a move, with Wiggins likely to perform better than him in Saturday's penultimate day time-trial.
But Wiggins, with able support from Froome, distanced Nibali on the finishing ascent.
Alejandro Valverde (Movistar) won the stage, Froome was 19 seconds behind in second place, with Wiggins on his wheel in third.
Nibali finished 37 seconds behind in seventh, conceding 18 seconds to Wiggins and falling 2mins 41secs behind.
Tomorrow's 222.5km 18th stage from Blagnac to Brive-la-Gaillarde features three classified climbs, but could end in a sprint finish.
Valverde led in the closing stages of the route as Wiggins took to the front of an eight-man group 4km from the summit of the day's final ascent, the 15.4km climb to Peyragudes.
Jurgen van den Broeck (Lotto-Belisol) attacked, increasing the pace, before Froome took to the front, keeping the tempo high.
The relentless pace saw the group disintegrate and Nibali lost contact 3km from the summit.
Froome forged on and Wiggins latched on to his wheel.
The Team Sky duo pushed on as their rivals lost touch and the Britons closed in on Valverde.
Froome implored Wiggins to keep up, eager to distance Nibali in his own bid to make it on to the podium - something no Briton has done before in 98 previous Tours.
Valverde passed through 2km to go with an advantage of 40 seconds and Froome continued to push.
Thibaut Pinot (FDJ-Bigmat) bridged the gap to the Team Sky duo, with Froome leading Wiggins and Nibali struggling to stay in contact.
Froome and Wiggins pushed forward as they finished second and third on the stage to enhance their places at the top of the general classification standings.
Pinot was fourth, three seconds further adrift, with Pierre Rolland (Europcar) fifth and Van den Broeck sixth, both 26 seconds behind Valverde.
Van den Broeck remained fourth, but fell 5:53 behind Wiggins.
The final mountain day of the 99th Tour was a late opportunity to eat into Wiggins' advantage.
Nibali made a short-lived move on the descent of the day's opening climb, the 9.3km category one ascent of the Col de Menthe, but was rejected by the seven-man breakaway group, who believed his presence would end their escape.
Thomas Voeckler (Europcar) had beaten Fredrik Kessiakoff (Astana), his nearest rival for the polka dot King of the Mountains jersey, to the top and did so again on the category two Col des Ares and category three Cote de Burs.
Nibali's Liquigas-Cannondale team led the peloton and kept the pace high on the fiendishly steep Port de Bales.
Four Team Sky riders and Wiggins were immediately behind.
Up ahead Valverde and his team-mate Rui Costa joined forces and forged forward.
Valverde powered on alone and went over the summit 2:25 ahead of the peloton.
Egoi Martinez (Euskaltel-Euskadi) and Costa, who made a wrong turn at the foot of the final climb, were in pursuit of Valverde as the peloton swept up the rest of the day's break.
The tempo set by the maillot jaune group saw Martinez and Costa caught and with Valverde the only rider up the road, Jelle Vanendert (Lotto-Belisol) made a late attempt to catch the Spaniard.
Defending champion Cadel Evans lost touch with the maillot jaune, leaving his BMC Racing team-mate Tejay van Garderen alongside 14 others.
Van den Broeck attacked with the peak of the Col de Peyresourde in sight, with Rolland and Pinot going with him.
Vanendert was quickly caught and Nibali, Wiggins, Froome and Chris Horner (RadioShack-Nissan-Trek) bridged the gap.
Pinot then took the initiative, stringing out the group in the mist before the short downhill section and the final 3.6km climb to the finish, where Wiggins and Froome enhanced their positions in first and second place overall.
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