Sebastian Vettel has admitted that former F1 supremo and friend Bernie Ecclestone helped him to negotiate his 2021 switch to Aston Martin.

"I really put pressure on team owner Lawrence Stroll to take Sebastian," 90-year-old Ecclestone, who is no longer F1 CEO, told Sport1 last month.

And in the last few days, F1 legend Gerhard Berger has said the quadruple world champion is interested in combining Formula 1 with occasional DTM races.

"It's true that I spoke with both of them, as well as some other people," Vettel confirmed in Istanbul.

"Some I consider my friends, some I just asked for advice. As for the commission, Bernie didn't ask me for it. I suppose he wouldn't like to take money from me," the German laughed.

As for potentially combining F1 with DTM, the German series that is headed by Berger, Vettel said: "In the past it was possible, but not today.

"I would be interested but when the calendar is going to 23 races, it's not so easy to find time. It's not really realistic."