Britain's Chris Froome won the 199.8km fourth stage of the Ruta del Sol on Saturday to overtake Alberto Contador and secure the leader's red jersey.
The Team Sky rider, who won the Tour de France in 2013, accelerated away on the 4.4km climb to the finish in Spain.
Froome, 29, now holds a two-second lead over Spaniard Contador (Tinkoff-Saxo) - who finished second - having trailed by 27 seconds at the start of the day.
Sunday's final stage runs 169.8km from Montilla to Alhaurin de la Torre.
"I'm absolutely blown away to have pulled that off at the end," Froome told Team Sky's website.
Stage four result:
1. Chris Froome (GBR/Team Sky) 5hr 08min 54secs
2. Alberto Contador (ESP/Tinkoff-Saxo) +29secs
3. Mikel Nieve (ESP/Team Sky) +49secs
4. Sylvester Szmyd (POL/CCC Sprandi Polkowice) +59secs
5. Benat Intxausti (ESP/Movistar) +1min
1. Chris Froome (GBR/Team Sky) 17hr 32min 16secs
2. Alberto Contador (ESP/Tinkoff-Saxo) +2secs
3. Benat Intxausti (ESP/Movistar) +2min 32secs
4. Mikel Nieve (ESP/Team Sky ) +2min 52secs
5. Romain Bardet (FRA/AG2R La Mondiale) +3min 13secs