Sergio Henao (Team Sky) beat fellow Colombian Carlos Betancur (Ag2r-La Mondiale) in a thrilling shoulder to shoulder sprint at the top of the steep climb to Trapagaran.

Henao caught Betancur in the final kilometre, when the road climbed to a painful 21 percent gradient. Betancur managed to hold his wheel and then come up alongside him in sight of the finish but Henao squeezed Betancur slightly and won by throwing his bike at the line. Giampaolo Caruso (Katusha) was third after sparking a late attack with Betancur.

Thanks to the time gaps opened on the rest of the field, Henao also took the overall race lead. Nairo Quintana (Movistar) is second at eight seconds, with Ritchie Porte (Team Sky) third at ten seconds.

Quintana finished eight seconds behind Henao, with Diego Ullisi (Lampre-Merida), Porte, Alberto Contador (Saxo-Tinkoff) and Simon Spilak (Katusha) all at ten seconds. They have the same time gap in the overall standings. Peter Stetina (Garmin-Sharp) finished 11th on the stage at 21 seconds. He is 16th overall at 26 seconds.

It was Henao's second win of the season after also taking a stage at the Volta ao Algarve in February.

"I had to dig deep to win," Henao said, flashing his dental braces through a big smile. "We knew the last 400 metres were very hard. Betancur was ahead and I had to give everything to beat him."

Team Sky has just six riders at the Vuelta al Pais Vasco after Ian Boswell and Joshua Edmondson did not start due to illness. However Henao isn't worried, confident that Porte can perform well in the decisive time trial stage.

"We will play two cards. Richie is going well and we know how strong he is against the clock. The important thing is that victory stays in the team. I feel good, I feel strong and I am motivated after this victory. We'll try and do everything we can."

How it happened

After two rolling stages in the hills that ended with select sprint finishes and back-to-back victories for Orica-GreenEdge, the 167.7-kilometre third stage to Trapagaran was always going to be decisive for overall victory, with the steep climb to the finish sure to create some time gaps.

With little chance of success for a breakaway, the attacks came from riders looking for mountain points and on the opening climb of the Alto de Zarate, Amets Txurruka (Caja Rural) went on the attack for a third day in row. He was wearing the climber's polka-dot jersey and is clearly on a mission to make sure Euskaltel-Euskadi understands they made a mistake by not extending his contract at the end of 2012.

With an early ramp up much like the Mur de Huy at Fleche-Wallonne, then a flattish section before the final wall to the finish, positioning was vital in the finale.

Saxo-Tinkoff rode to protect Alberto Contador, while Ryder Hesjedal (Garmin-Sharp) hit the front and even went on the attack, to set-up Peter Stetina and Andrew Talansky. Team Sky was also there in numbers, as were Lampe-Merida, with Damiano Cunego and Ullisi.

Henao tested his rivals mid-way up the six kilometre final climb but Contador marked him, trying to control the racing. Betancur and Italy's Giampaolo Caruso (Katusha) got away over the top of a steep section and on a brief descent with three kilometres to go in a desperate attempt to anticipate the late surges to the line. However a front group of 30 riders formed behind them and closed in as they hit the 21percent section of the climb to the finish.

Henao was the only rider able to get across the 30 metre gap to the two leaders and that allowed him to fight for victory.

He looked set to pass Caruso and Betancur but the Ag2r-La Mondiale rider managed to follow him and then match him as the line approached. In almost a slow motion sprint, the two touched arms and shoulders several times as they fought the gradient. Henao won by squeezing Betancur slightly, forcing him to ease off on the pedals. In contrast Henao made a lunge for the line as if doing a track sprint and won by half a wheel. Betancur protested slightly but knew he had been beaten.