German Vettel, the world championship leader and Sochi pole sitter, is out of contract at the end of this year.
As for the rumours of a Mercedes switch, however, team chairman Niki Lauda told ORF: “That’s nonsense.
“Why should Vettel leave Ferrari now that he wins one race after another? It would be crazy,” he added.
But according to the rumour, Mercedes sees Vettel as an ideal long-term replacement for fellow German Nico Rosberg, who retired at the end of last year.
Rosberg’s current successor, Valtteri Bottas, has only a one year contract.
“It’s very early to talk about a renewal for Valtteri,” team boss Toto Wolff told the Italian broadcaster Sky.
“But I like him a lot and he’s going well. As for the rumours about Vettel, I think at the moment he has the fastest car, and when you have that, you don’t change.”
But if Ferrari does have vacancies for 2018, another rumour is that Max Verstappen is first in the Italian team’s sights.
However, Red Bull’s driver manager Helmut Marko told Auto Bild: “Contrary to rumours, there is no performance clause in Verstappen’s contract.
“If we do not release him, he cannot go to Ferrari.”