Renault insists its engine partnership with Red Bull can last long-term despite rumours Audi is in talks with the drinks company about an F1 project.

Red Bull and Renault won four titles together under the previous set of regulations, but have struggled for performance and reliability since the current V6 turbo engines were introduced last year. Red Bull has put the blame firmly on Renault and after the Spanish Grand Prix said Helmut Marko said he is looking to Audi as a potential engine partner in the future.

However, speaking during the Spanish Grand Prix weekend, Renault Sport F1 managing director Cyril Abiteboul said the "marriage" with Red Bull is salvageable.

"We are here for the long-term but we are living through a tough moment," he told Formula One's official website. "Is there a better wife for Red Bull and Toro Rosso out there? I don't know. Is there a better husband - if it is in this direction - for Renault? I don't think so.

"This marriage has all the reason in the world to last. So we have to do a better job on-track, but we also have to a better job off-track ... and maybe in bed also."

Abiteboul said the Renault power unit is showing potential on the dynos back at the factory, but something is preventing that translating into on-track performance at races.

"On the dyno the engines are reliable, but when we come on track they are not. Obviously there is something wrong in our validation process, from dyno to track in terms of testing. There is something we need to investigate. It's just like aerodynamics, when the wind tunnel is not telling the truth; it's exactly the same in the engine world.

"Maybe we flattered ourselves on the back of very good results with Red Bull for years, to think that we are controlling everything. But maybe there was some form of beast in the shadows, hiding. And we need to hide that beast now.

"We need to set ourselves realistic objectives. We know sometimes our customers will not like it ant that's one of the difficulties of operating as a supplier to customers, and I'm pretty sure if we were one team we would be capable of managing this crises, including at a human level in a better way."