Three-week gap between F1 races 'critical for Renault - Red Bull

Renault is understood to be redoubling its efforts to raise its game with the chances of creating its own works team now fading, and there will be further improvements for the Spanish GP.

The French manufacturer had not originally planned a major step in Spain, but following its troubled start to the year there is pressure within the company to do so.

"For Barcelona we will be bringing a few bits and pieces, as will all the teams," said Horner when asked about car upgrades.

"The significant thing for us is what specification of engine will we have in Barcelona, because it's a bit earlier than Renault had in their plan for the next step.

"I think the next couple of weeks are going to be critical."

Horner confirmed that he visited Renault in Paris between the Chinese and Bahrain GPs to discuss progress on the engine.

He is confident that the company is willing to commit the resources necessary to close the gap to Mercedes and Ferrari.

"I went to Paris last week and I had a very constructive discussion with Jerome Stoll, the board member who F1 sits under," said Horner.

"They don't want to be in this position, they want to be in F1 to compete and to win.

"Of course, that's not going to be done for free. He recognises that and Renault seems committed to finding a solution."

AUTOSPORT understands that Renault is willing to increase its level of investment in the F1 programme to achieve this.

But there are still question marks over the development direction, with Mario Illien, who is working with Renault as part of a deal initiated with Red Bull, having isolated some potential areas of improvement independent of the marque's own programme.