Red Bull Racing boss Christian Horner says moves to ensure there is engine parity in Formula 1 next year are vital - with the issue stalling his team's new supply deal with Renault for 2010.
The Milton Keynes-based team is still waiting for confirmation about its engine plans for next year - despite having Renault listed as its 2010 partner by the FIA earlier this week.
The official 2010 entry list published on Monday said that Red Bull Racing would be supplied by the French car manufacturer - something that appeared to rule out a switch to either Cosworth or Mercedes-Benz.
However, Horner has revealed that despite submitting Renault as its proposed engine supplier next year, Red Bull Racing still does not have a contract in place.
He thinks it will take at least another week before the situation becomes clear - with a decision about F1 engine parity key to the matter.
It is understood that one of the topics up for discussion in next week's Formula 1 Commission meeting is whether anything needs to be done to ensure all engines are equal in performance.
The FIA said earlier this year that if teams agreed action was needed to make engines more equal, then it would be open to changing the rules.
Speaking to AUTOSPORT about the situation, Horner said: "I wouldn't read too much into the entry list. We're obliged to put an engine as per the regulations. But we are allowed to change the engine at any point up until the first race.
"Obviously we have to put an engine on the list and the most likely engine to have in the car next year, at this moment, subject to Renault's confirmation, is a Renault engine. We have to put engine on the list, and that's the logical choice so far."
Horner revealed that Renault is reluctant to commit to the deal, however, until it knows exactly what the plans are for engine parity in 2010.
"We've enjoyed three good working years with them," he said. "They're a very good partner and it's been a very successful collaboration with them.
"They've supported us well through difficult times this year, particularly with Sebastian Vettel's car, where we've had to limit the engine mileage. They obviously have concerns over engine parity at this point in time, and until engine regulations are clear, I can understand a hesitation on their side."
He added: "I think it depends on what's done with the engine regulations moving forward in terms of parity. The teams have decided that the engine should not be a performance differentiator under the frozen rules. I think it's vital, not just in the case of Renault, but in the case of all the engine manufacturers, that a solution is found."
Despite not yet having a Renault deal in place, Red Bull Racing is not actively chasing other options.
A move to Mercedes-Benz, which had been close at one stage this year, was blocked by McLaren, while Horner has also now played down the chances of a switch to Cosworth either.
"At this stage, realistically no," he said when asked if Cosworth was an option. "In principle we have an agreement with Renault and hopefully in the next week or so everything will be finalised."