Ross Brawn has admitted Mercedes' new 2012 car is not ready to take on the best teams in formula one.

"We are slower than Red Bull; we need to find more speed," the Briton plainly told Germany's Auto Motor und Sport.

Other team figures for the German marque's Brackley outfit this week said the target for 2012 is third place, with the title not a realistic goal until 2014.

"On the positive side, our car is reliable and it's a step forward, but we are still not where we want to be," added Brawn.

He confirmed that the goal for 2012 is to finish behind the top title challengers.

"Third place, one better than last year," said Brawn. "Anything better than that, of course, is welcome."

He said Mercedes has been aggressive with the design of the W03, "But we have not reinvented the racing car".

"Red Bull has the advantage of building on a very good foundation."