Mercedes motorsport boss Norbert Haug admits that Red Bull Racing was wise to secure reigning F1 world champion Sebastian Vettel to an extended contract, even though his employer had not shown interest in the German for a couple of years.

Vettel will remain a Red Bull driver for at least another four years, having inked a contract extension that takes him through to the end of 2014 and prolonging a relationship that began back in 1998 when the drinks brand all but saved his racing career by funding him through the junior formulae.

Not that Mercedes hasn't been interested in finding one of its 'countrymen' to fly the Three Pointed Star before landing the Nico Rosberg-Michael Schumacher combo for 2010. Red Bull advisor Dr Helmut Marko remembers the German giant attempting to pair Vettel with Lewis Hamilton at the Mercedes-powered McLaren team for 2009 as an alternative to Heikki Kovalainen, but confirms that there have been no approaches since then.

At that time, Vettel was coming off his first full season in the top flight, marked by an historic victory for Scuderia Toro Rosso in tricky conditions at Monza. McLaren, en route to the title with Hamilton, was expected to be his closest rival that afternoon, but the Briton erred in qualifying and Kovalainen could do nothing with a front row position alongside the STR entry.

With Mercedes now an F1 entity in its own right, having bought the title-winning Brawn team ahead of the 2010 season, many expect Vettel to be as big a target for Haug as he appears to be for Ferrari, but the burly German insists that there has been no move for his compatriot since the 2009 bid.

"Since then, there was no more [offers]," he said in a joint Bild interview with Marko, "Red Bull would have made a big mistake not to secure him for the long term."

While Vettel has made no secret of his interest in one day racing for Ferrari, Haug admits that signing a new deal with RBR was the best thing the German could have done, and concedes that Mercedes would not be a viable option just yet.

"[RBR] are able to offer him the very best equipment at the moment and we're not quite there," he confessed.