Vettel cautious on Red Bull's form

The German was comfortably clear of the opposition on the first day of this week's test at Jerez in Spain which, on the back of some quick performances in earlier running, has left some rivals convinced Red Bull Racing could be poised to spring a major surprise.

But Vettel insists he is keeping his feet on the ground - and has laughed off talk that Red Bull are on the verge of taking the fight to McLaren and Ferrari for title glory.

When asked if he felt ready to launch a championship challenge this year, Vettel said: "Ha! If you are speaking about that, then everything needs to be in perfect shape and running smoothly.

"We are not the favourites - the favourites are red and silver - they are Ferrari and McLaren-Mercedes. It is a long way to get to that position, but we are working hard. We have great potential, the car seems to be alright so let's see. If we have a package that is strong enough to win, then we have to win - otherwise we are doing a bad job."

Vettel believes that it is dangerous to read too much into pre-season testing times - and says the experience of Williams last year is evidence about how a good build-up to the year does not guarantee performance in-season.

"Williams were looking very, very strong (in pre-season testing) and in Australia they finished on the podium, and a couple of weeks later no one was speaking about them any more.

"So winter testing, you always have to keep your feet on the ground. There are a lot of things coming for everybody. There are new bits for Australia, so we have to wait until then."

Vettel did say, however, that Red Bull Racing were working hard on making further improvements to their car to lift their performance in readiness for the start of the season.

"The team is pushing very hard," he said. "The whole design crew is working hard - and our car from the outside looks quite nice, but still we have to prove that it is fast as well.

"The feeling is alright, the performance seems to be alright, but we will see in Australia. We will get some new bits hopefully for Barcelona, if not for Australia, but how much of a step in the right direction that will mean we will wait and see. You always have some numbers but you have to prove it on the circuit."