Red Bull's 2016 F1 participation in jeopardy amid engine wrangle

The four-time champion team would now appear to be solely reliant on securing a deal with Ferrari for 2016 and beyond.

Red Bull is understood to have served notice on its contract with Renault, and Mercedes has decided against being its supplier.

Ferrari team boss Maurizio Arrivabene recently stated the Scuderia would have no problem in supplying Red Bull, although a final call would have to come from chairman Sergio Marchionne.

AUTOSPORT understands suggestions of Red Bull taking on a year-old spec of power unit are wide of the mark as it naturally wants to be competitive with a new supplier from the off.

Asked by AUTOSPORT as to his team's chances of still being in F1 in 2016, Horner replied: "That depends on the desire of other parties for us to be in Formula 1.

"If we don't have an engine, we can't compete.

"Dietrich [Mateschitz] has always made it very clear he wants to have a competitive engine."

Mercedes was initially Red Bull's preferred option, but the board decided over the course of the Italian Grand Prix weekend a fortnight ago against working with a team it felt would have become a major championship rival.

Horner conceded to being neither surprised nor disappointed by the decision.

"On the one hand you can understand Toto [Wolff, Mercedes motorsport boss] in that they see Red Bull as a threat," he said.

"They're probably not that keen to see one of their biggest assets supplied to a competitor. Toto made his position pretty clear.

"To be honest, we expected it. Toto, from the word go, was never a fan of supplying Red Bull. It was his board that was perhaps more interested than he was.

"But it's not an option, so now we focus our attentions elsewhere."

Renault CEO Carlos Ghosn remarked this week the contract with Red Bull was being "renegotiated".

Ghosn added Renault would no longer be an engine supplier, though it would at least honour its deal for 2016 with Red Bull and Toro Rosso - if the teams wanted its power units.

Asked how far down the line negotiations were with Ferrari, Horner replied: "Before discussing any other engine scenario it's important for us to understand what Renault's plans are for 2016. They seem to be formulating.

"We will be sitting down with Renault to discuss that before committing or having anything else to talk about publicly.

"So for us, first of all, let's focus on understanding what the Renault situation is, and then we can really address what our options are for the future.

"But if you want a competitive engine it's obvious you're pretty limited."