Saxo Bank-Tinkoff Bank rider Contador, a former winner, attacked with 3 miles to go on the final climb. But Rodriguez caught and passed his fellow Spaniard to win the 93-mile mountain stage that featured five category climbs.

Rodriguez finished in 4 hours, 10 minutes, 28 seconds, extending his advantage over Contador to 22 seconds.

"Today I showed that I am also strong in the long climbs, although I recognize that in some moments I had trouble keeping up because Contador's attacks were incredible," Rodriguez said. "I arrived dead at the finish, but I thank my team for all their work because the pace was very hard."

Alejandro Valverde of Movistar was third, followed by Rodriguez's Katusha teammate Daniel Moreno and Christopher Froome of Team Sky.

Both Valverde and Froome attempted late charges but faltered in the final stretch and trail Rodriguez overall by 1 minute, 41 seconds.

Even so, Rodriguez doesn't count either rider out.

"There are several demanding stages left and the duel isn't just between Contador and me," Rodriguez said. "I think Valverde and Froome are very close and either one can go for it."

Riders face more mountain stages on Sunday and Monday. The stage Sunday covers 116 miles from La Robla to Lagos de Covadonga.

The 21-stage, three-week Vuelta a Espana finishes in Madrid on September 9.