Contador won 10 stages on his way to the 2009 Tour de France title
Alberto Contador launched a stunning hill attack to take the fourth stage of the Paris to Nice race, as he prepares to defend his Tour de France title.
The Astana rider made his move with just two kilometres left of the 173.5km stage, finishing 10 seconds clear of second-placed Alejandro Valverde.
Contador, 27, now leads the "Race to the Sun" by 24 seconds from Valverde, with three stages remaining.
"I am satisfied, but it was a difficult day," the Spanish rider said.
"I wasn't sure what the best tactics were but I tried and made the difference. Now, the race is on but there are still three difficult days ahead."
The 2009 Tour de France champion, who will start his defence of the title on 3 July, had been 20 seconds behind German rider Jens Voigt overnight, but Contador's impressive display saw him assume the yellow jersey.
The Astana and Saxo Bank teams had fallen behind from a breakaway group which racked up a lead of almost four-and-a-half minutes.
But Valderon's team fought back, catching the lead pack with 15km remaining, and no one could match the two time Tour de France winner's pace over the final ascent.
Fellow Spaniard Luis Leon Sanchez came in third, while overnight event leader Voigt crossed the line 44 seconds off the pace, slipping to sixth overall.
Czech rider Roman Kreuziger, who lies in third place overall, finished the stage in seventh place and 25 seconds behind the race leader.
Garmin rider David Millar finished the stage ninth in the overall standings, one minute and three seconds behind Contador.