It is now being rumoured that F1's rival top teams are in fact considering huge sums of money to tempt Verstappen, who is under contract at Red Bull for 2018 and 2019.
Marko told Bild am Sonntag: "I'm not worried. Max started with us and he wants to get his first world championship with us. That is our desire as well."
It is rumoured, however, that Mercedes's interest is not just one way.
Marko commented: "Herr [Toto] Wolff talking with father [Jos] Verstappen is just typical Formula 1. I am not sleeping badly."
Verstappen is currently sixth in the driver standings.