Red Bull team principal Christian Horner says once again that Red Bull boss Dietrich Mateschitz could withdraw from F1 if he does not like how the rule changes proposed for 2021 affect the sport.

The end of the Concorde Agreement in 2020 means that the sport could be in limbo with a lack of clarity and direction. The proposed rule changes for 2021 are also tied into the Concorde Agreement and will need the agreement of the current F1 teams, the FIA and the Formula 1 Group.

Liberty Media has made it clear that the preferential deals that were set up by Bernie Ecclestone including Red Bull, will not be renewed and that all the teams will have to accept a level playing field.

Red Bull does not want to see budget restrictions introduced as they have concerns about where a spending cap would leave them as an independent team without in-house engine suppliers.

Horner said of Mateschitz: "He's passionate about motorsport, he's passionate about F1, he's enthusiastic about the new engine partnership with Honda and the potential that brings. But of course, F1 has to deliver for the Red Bull brand as well.

"It needs to be exciting, it needs to be cost-effective, the racing's got to be great and we need to be able to play on an equal and level playing field with OEM and manufacturer teams."

Horner then added that he thinks that Mateschitz is waiting to see what happens to F1 post-2020. He did temper the comments by saying that Mateschitz is tremendously supportive and has probably invested more into F1 than any other entity.

"Two F1 teams, a Grand Prix (Austria) plus all the promotion that Red Bull does around the world supporting F1, Its enormous. He wouldn't do that if he didn't believe in the sport."