Renault says its relationship with Red Bull should have been a perfect fit, but admits a split at the end of 2016 is likely if an unwillingness to work together continues.

The contract between engine supplier and team is set to expire at the end of 2016 and it is looking increasingly likely the two will not renew their deal. The cracks in the relationship have been obvious since the opening round of the season when Red Bull publicly slated the Renault power unit and the French manufacturer started reconsidering its position in the sport. Renault is now seriously evaluating a deal to set up a works team, while Red Bull has been linked to a Mercedes engine deal in an attempt to return to the front of the grid.

Renault Sport F1 managing director Cyril Abiteboul admits the power unit has not been a match for its rivals, but believes part of the reason is because Red Bull did not follow through on its promise to work with Renault as a single works team.

"They expressed a desire, but for some reason - and maybe the reasons are not completely on their side - we have not managed to move from the uniform statements to acts," Abiteboul told ESPN. "It's one thing to state that Red Bull is our team and a works team of Renault, but it's another to make it happen.

"When you are a works team, for example Mercedes, it has one budget. At the start of the year the first decision that they have to make is how much is going into the engine side and how much into the team side and in order to do that you look at the regulations, you look at your overall performance and you look in particular at the break down in performance between chassis, engine and driver. You make your plans and distribute the money and budget that you have available between those three elements. For me it's a no brainer and that should be the way forward."

Red Bull and Renault won four drivers' and four constructors' championships together under the V8 era when engine development was frozen, but Abiteboul said the relationship did not change enough in 2014 to reflect the extra investment and support needed to develop the current V6 turbo power units.

"You can afford to think differently and act differently when the engine is frozen because our engine costs were much lower, but when there is an arms race in engine technology and the return on money spent is higher on the engine than it is going to be on a front wing then you have to review the whole economic view.

"Okay, frankly, we are not where we want to be from an engine perspective, but I don't think the blame is entirely on our side, I think it's much more complex. I don't want to play the blame game, but clearly the association we have with Red Bull is of use to them and of use to us, but it does not work and does not deliver any more.

"In my opinion it is related to the fact that the evolution of the engines has dramatically changed and the kind of relationship that we could afford to have, which honestly was not very sophisticated, was possible when the engine was frozen, but is not possible any more. In a context where the engine is not frozen and there is a bit of an arms race on engine technology, you can't have the engine partner on one side and the team on the other; it doesn't work that way anymore.

"If we want to have a long-term presence in F1 we have to change this model. Frankly, I would have thought it could be possible with Red Bull, it's in their interest and it's in our interest. So if it is possible with Red Bull fantastic, but if it's not possible they will have to find a different way forward and we will have to find a different way forward after 2016."

Abiteboul believes a Red Bull/Renault split will represent a "huge wasted opportunity".

"Theoretically there was a way forward. I think they are a brand that in many respects is a fit for our customers. We are Renault, we are not posh, we are not elitist - we are about energy, we are about dynamism and being able to afford a decent lifestyle to a young generation of people.

"So in many respects there is a brand fit, which is why if we don't manage to find a way forward it will be a huge wasted opportunity. What we want to get is to get control, control our communication, control our brand, to control our technical road map and control our performance - why we perform and why we don't perform."