Vettel's 2014 contract 'bullet-proof'

(GMM) Dr. Helmut Marko on Thursday dealt a blow to the persistent rumors about Sebastian Vettel's future.

Some in the paddock believe the German has signed some sort of agreement that could see him switch from Red Bull to Ferrari in 2014.

German reports recently added fuel to the fire by acknowledging that while the reigning back-to-back world champion has a Red Bull contract for 2014, it contains some 'get out' clauses.

But Red Bull's Marko told Sport Bild: "I have to disappoint Ferrari and all the others.

"Sebastian has a bullet-proof contract with us through 2014. There are and there have never been any options or opt-outs," the team's driver manager insisted.