Red Bull's Helmut Marko remains convinced that F1 needs to attract independent engine suppliers even if another manufacturer joins the fray in the coming years.
Porsche's LMP1 retreat from the WEC has fueled speculation that the Weissach manufacturer - or another brand of the Volkswagen group - could eventually answer F1's call, even as it commits to Formula E in 2019.
"For us it is currently more important that independent engine manufacturers such as Aston Martin, Cosworth or Illien are present in the negotiations," Marko told Welt newspaper.
"What we see with Honda is that even with the highest financial and personnel expenditure, it is not possible to have success with these very complex engine regulations."
In the interim, Red Bull Racing's form is on the rise as the Milton Keynes-based outfit develops its RB13 chassis and engine partner Renault also improves its power unit.
"From a technical point of view, the chassis is at a very high level compared to Ferrari and Mercedes," said Marko.
"Our engine partner Renault is making continuous progress, which means that Red Bull will win one or two races on its own strength this year," he added.
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