The Movistar cyclist made a big push toward winning the 52nd edition of the race by finishing the 151-kilometer (94-mile) ride nine seconds ahead of Olympic champion Samuel Sanchez, the overall leader after the third stage.

Luxembourg's Frank Schleck and the Netherlands' Wouter Poels tried to get ahead in the last kilometer of the steep, final ascent, but Rodriguez controlled before counterattacking with 500 meters to ride. Rodriguez crossed the line alone in 3 hours, 55 minutes, 56 seconds to also hold a nine-second overall advantage over fellow Spanish cyclist Sanchez.

"It was a really hard final part, but very suitable to my characteristics," Rodriguez said. "First, I was able to slipstream Schleck (and) then Poels, then I managed to pass him and win." Sergio Luis Henao of Colombia and Robert Kiserlovski of Croatia both crossed the line 12 seconds later, while Lars Petter Nordhaug of Norway led a group 16 seconds behind in fifth.

Rodriguez leads his Euskaltel-Euskadi rival with an overall time of 16:02:02, which is 21 seconds better than third-placed American Christopher Horner of RadioShack-Nissan. Kiserlovski and Henao trail the leader by 24 seconds.

The next-to-last stage on Friday is a 183-kilometer (114-mile) cycle from Bera to Onati, before Saturday's time trial finale.

"Races against the clock are not my specialty, but this one will be quite technical, with many ups and downs. It won't be a classic time trial," Rodriguez said. "Now I have a nice gap so I think I have some chances, at least, to (win)."