By Julien Pretot
L'ALPE D'HUEZ, France (Reuters) - Chris Froome is poised to win a second Tour de France title, but was forced to hang on desperately as Colombian Nairo Quintana attacked relentlessly in Saturday's penultimate stage up the iconic Alpe d'Huez.
In a gripping finale, Quintana powered clear of Froome, slicing almost a minute and a half off the Briton's lead, but not doing quite enough to prevent the Team Sky rider almost certainly ensuring he will celebrate victory on Sunday.
With only the procession into Paris remaining, Froome leads Quintana by 1:12 after the Movistar rider attacked repeatedly and pushed the 30-year-old to the limit in a punishing ascent.
The day's laurels went to Frenchman Thibaut Pinot, who salvaged an under-par Tour with victory on the race's 'Queen stage'.
Spain's Alejandro Valverde is third 5:25 off the pace.
Quintana was second in the 110-km stage from Modane-Valfrejus, 18 seconds behind Pinot, with Canadian Ryder Hesjedal taking third place 41 seconds adrift.
Froome, who could not respond when Quintana attacked less than four kilometers into the 13.8-km ascent, ended the stage in fifth place, 1:38 off the pace after being helped to the summit by team mate Richie Porte.
Froome, who claimed his first Tour title in 2013, was once again booed by the crowd in the final climb.
He will become the first rider since Carlos Sastre in 2008 to win both the yellow and the polka dot jerseys -- although the Spaniard only claimed the mountain classification after Austrian Bernhard Kohl was stripped of the title following a retroactive dope test.
Froome, who had already lost 30 seconds to Quintana on Friday, spent another tough day in the saddle.
Frenchman Alexandre Geniez attacked from the start and broke away with three others but the FDJ rider went out on his own in the climb to the Col de la Croix de Fer.
Among the group of favorites, Valverde attacked about five kilometers from the top of the col de la Croix de Fer and was quickly followed by Quintana.
Helped by Porte, Froome managed to catch Quintana at the top and along with Valverde and Nibali, the four of them stayed together in the descent.
Pinot and Hesjedal then attacked and the Frenchman, who got help on the way from his FDJ team mate Geniez, powered to his second Tour stage win after claiming his first on his debut in 2012.
(Reporting by Julien Pretot; Editing by Toby Davis)