Red Bull’s Christian Horner has said that he is worried that Renault and Honda won’t be able to catch up to Mercedes and Ferrari before F1’s engine rules reset in 2021.

The Mercedes and Ferrari works teams having been dominating all season and the Renault powered Red Bull is third with less than half of the points of the Constructors’ Championship leaders.

The Renault and Honda engines have had reliability problems all season and Horner thinks that both manufacturers will continue to struggle to close the power gap.

“We’ll never accept that we can’t be competitive so we’ll keep pushing and keep developing and try and make up whatever horsepower deficit there is on the chassis side,” the Red Bull team boss told Sky Sports F1.

However, he went on to say that Ferrari and Mercedes “have such a march, such committed investment” that it is “difficult to see how the others will catch up in the intervening period between now and 2021.”

Horner has been a consistent critic of the hybrid turbo engines that were brought in in 2014 and at the Italian GP he said that the engines “has done nothing positive” for F1.

F1 has committed to keeping the engines until 2020 and there have been ongoing talks about the next generation of rules.

There are calls to make the next engine formula cheaper and less complex and this has resulted in Porsche confirming their interest in returning to the sport as a supplier. Horner also thinks that Aston Martin and Lamborghini could also be tempted.

“We may well [lose manufacturers] but I think there are iconic manufacturers who would be keen to come in if it was affordable,” said Horner.