Vettel vows to fight on for title

The German's retirement - as a result of his second engine failure of the weekend - was a massive blow for the winner of two grands prix this season. He is now 25 points behind Jenson Button in the title race with six rounds to go.

"It's not good," he said. "In terms of the championship, I will fight until the last breath, but it's not good to have retired when you're hunting and want to get more points than your opponent.

"You're in a position to do it, but then you don't finish the race."

Vettel wasn't in a position to take points on Sunday in Valencia after a fuel rig problem rendered him 16th following a required second stop.

"The biggest problem today was the first stop - we weren't able to get fuel in the car, so we had to come in again. We were lucky to make it back for a second stop.

"The race was lost already at that point but then, a couple of laps on, I had a problem with the engine and I had to retire."

Red Bull team principal Christian Horner admitted that the failure had been expensive but that while it made Vettel's title hopes more difficult to achieve, he was still in the fight.

"We need to look into and understand that, but it is an expensive failure," Horner told the BBC.

"He's always in it [the championship] until mathematically it's impossible to win. It's increasingly difficult, especially with a handicap of only two engines left between now and the end of the year. It puts us under quite a bit of pressure."