Red Bull has once again threatened to quit Formula One if it's not provided with a competitive engine.
The four-time constructors champions will stop using units supplied by Renault and is in talks with Ferrari for the 2016 season.
But Red Bull will not accept an engine from the Italian company if its performance is worse than the one used by the Ferrari F1 team.
"For those among us who have listened closely to what Red Bull chief Dietrich Mateschitz and his motor sports consultant Dr. Helmut Marko said recently and who interpret it correctly and put together one and one, a clear scenario emerges: Red Bull Racing and Scuderia Toro Rosso will pull out of Formula One after the 2015 season," said Red Bull in an article in their Speedweek publication.
"Red Bull doesn't want to have customer engines that have 30 to 40 bhp less and can be manipulated by the constructor in case of the customer team endangering the works team. Red Bull would like to continue in F1 only if Ferrari is willing to provide true works engines that are on the same level as the engines of Vettel and Raikkonen."
Red Bull won the driver and constructors champions four years in a row from 2010 to 2013 with Sebastian Vettel taking the individual crowns.
This season, Daniel Ricciardo and Danil Kyvat are 7th and 8th respectively in the drivers' standings.
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