Red Bull's hopes of landing Mercedes engines in 2016 appear to be all but over, Motorsport.com understands, with the car manufacturer's top management now convinced such a deal would not be good for its Formula 1 team.
As Red Bull considers its options for next year amid the breakdown of its relationship with Renault, its focus had been on winning over Mercedes about the benefits of a tie-up.
Sources suggest Red Bull was hopeful that, despite its rival team's management not being in favour, the Mercedes board could be won over because of the attractiveness of a tie-up with the energy drinks brand.
However, it is understood that Dieter Zetsche, chairman of Mercedes parent company Daimler, has gone cold on the idea following talks with Mercedes motorsport management representatives Toto Wolff and Niki Lauda at the Italian Grand Prix.
Without his support, and the F1 team against, there is very little hope of a deal being pulled off should Red Bull make a formal approach.
Too many negatives
Mercedes has not spoken about its latest thinking, but only last week Wolff suggested that he was increasingly concerned about the negatives of a Red Bull partnership.
"If I judge it from the perspective of our team, it is an agreement that you should not do," said Wolff. "Our car and our successes are the result of hard work and huge investment from Daimler.
"We built our supremacy, while today there is a team that has decided that they do not want to stay with their partners. It is a different philosophy to ours.
"Nothing has happened yet, because we do not look so much at the possible benefits of the deal, as to the negative arguments that are likely to be more for our team."
It is those competitive concerns – that Mercedes would wipe out one of its performance advantages by giving engines to Red Bull – that are believed to be key in Zetsche's mind now too.
Furthermore, there are worries about the potential brand damage should Red Bull ever complain that it was not getting equal treatment if it was beaten
Ferrari now only option
It appears that only a dramatic last-minute change of heart will now be able to save Red Bull's hopes – but without Zetsche's support there seems little chance of it happening.
As was widely reported at the Belgian Grand Prix, Red Bull has notified its current engine partner that it wants to terminate its contract on performance grounds.
Although such a way of terminating the deal has been questioned by Renault – who insist there is no get-out clause – sources suggest that the French car manufacturer will not force Red Bull to stick out the partnership if it wants out.
Red Bull boss Christian Horner said after the Italian Grand Prix that his company was still awaiting an answer from Renault about its future plans though.
“Time is starting to press on now,” he said. “We are now into September and everyone needs to know what are Renault’s plans for the future. within the next two weeks. We should all know what Renault’s position is.”