F1-Insider report that there is “a civil war” inside the F1 constructors’ champions ahead of the United States Grand Prix this weekend.

“Just being team boss at Red Bull is no longer enough” for Horner, it is reported.

He wants to “get rid of” Helmut Marko and be in sole charge of Red Bull and its sister team AlphaTauri.

Marko was a key ally of Red Bull founder Dietrich Mateschitz, who died a year ago, and still retains the backing of new boss Oliver Mintzlaff.

“Horner had planned and is still planning the coup,” it is remarkably reported.

It is claimed that he sought support from Red Bull’s 51 percent shareholders from Thailand before attempting to recruit Bradley Lord - Mercedes’ chief of communications who acted as Toto Wolff’s stand-in at the past two grands prix - as new team principal of AlphaTauri.

That plan did not work.

Horner lent support to Peter Bayer, new CEO of AlphaTauri. But the addition of Laurent Mekies to AlphaTauri was Marko’s call.

Horner’s “role was discussed” in a meeting between Marko and Mintzlaff, the report claims.

Mintzlaff will be in the paddock in Austin this weekend.

Max Verstappen has pledged his loyalty to Marko in conversations with Mintzlaff already.

Horner responded to these claims by telling Mirror Sport: "Without Helmut, I wouldn't be in the position that I am today.

“Like with the young drivers that he has given an opportunity, he also gave me that opportunity. 

“We've always enjoyed a very strong and open relationship. Of course, there are things that we disagree on now and again, but I think that's healthy.”