Red Bull Racing team principal Christian Horner insists he won't use the European Grand Prix as a basis for deciding on a potential split with engine suppliers Renault following a weekend in which they suffered two costly failures.

Sebastian Vettel has fallen 25 points adrift of Jenson Button in the Formula 1 World Championship driver standings after seeing a potential podium finish scuppered by an engine failure - his second of the weekend.

Marking a fourth engine blow of the season for the Renault-powered RB5, Horner admits he is frustrated by the problems, claiming the team is now prepared for a future penalty due to the fact they are running out of engines to use.

"It doesn't get much worse than losing another engine and going back home with no points for either driver," he told the official Formula 1 website. "It is really disappointing for Sebastian, who had two engine failures over the weekend - the fourth now in total - which makes it quite difficult with the engines for the rest of the year.

"It's almost inevitable that we will have an engine penalty at some point because yes, we're running out of engines. We need now to analyse the mileage that we've left on the engines that we have and look at which engine we will use at what circuits."

Coming at a crucial time when Red Bull are in the midst of firming up their plans for F1 2010, while it has been confirmed Vettel and Mark Webber will stay on for next year, it remains to be seen whether they will extend their contract with Renault for an engine supply.

Nonetheless, despite being 82.5 points up on their factory counterparts, Horner says he will not use one bad weekend as a prompt for an imminent decision.

"I think it is still a long way to go in this championship and obviously our options are open. But you cannot make a decision based on one weekend, you have to look at the whole season and Renault so far has given us a great service and support. It was really unfortunate to have two engine failures in one weekend."

Furthermore, reports in Bild and Austrian newspaper Salzburger Nachrichten suggest that Red Bull are considering an option from Mercedes-Benz to use their power in 2010.

"There are good arguments for both the extension with Renault and for a change to Mercedes," Red Bull motor racing advisor Helmut Marko said.

"The two engine failures for Vettel at Valencia will play a role in deciding, particularly as all six Mercedes drivers have had no engine failures this year."

Mercedes-Benz currently supplies customer engines to championship leaders Brawn GP and Force India, as well as long-term partners McLaren.