LONDON (REUTERS) - Formula One manufacturers are sceptical about a proposed new power unit from 2021 because of the "immense" costs of development, Mercedes motorsport head Toto Wolff said on Wednesday (Nov 1).

Formula One's new US-based owners Liberty Media and governing International Automobile Federation (FIA) presented their 'road map' for the future to the 10 teams in Paris on Tuesday.

"This is their vision and proposal and we haven't accepted it. The flaw of the concept is that it's a completely new engine and new investment," Wolff told the BBC.

"It portrays it in a way of this is how we're going forward and none of the current OEMs (Original Equipment Manufacturer) was particularly impressed," added the Austrian.

Mercedes, Ferrari and Renault each supply three teams while Honda will be with Toro Rosso next season.

The powers-that-be are hoping to entice new suppliers after 2020 by making the V6 turbo hybrid power units simpler and cheaper as well as higher-revving, and therefore noisier, to satisfy fans unhappy about the current muted sound.

They also hope to reduce the gulf between the wealthy manufacturer teams like Mercedes and those privately-owned outfits who have to pay for their engines and have far smaller budgets.

The current commercial agreement with teams expires at the end of 2020, which means some existing manufacturers could walk away without penalty rather than accept heavy developmental costs and reduced revenues.

Red Bull principal Christian Horner, when asked in Mexico at the weekend what the likely response to the presentation would be, said he expected "a lot of filibustering" over the coming months.

Horner has been a big critic of the current power units, with Mercedes dominant for the past four years while teams like Renault-powered Red Bull have struggled with performance and reliability.

Wolff's comments indicated there would be plenty of resistance to overcome.

"The new concept needs to tackle the deficit that has been outlined - development costs and noise level - and all that needs to be linked with a global view of F1. We haven't seen any of that," he said.

Renault F1 motorsport head Cyril Abiteboul told France's L'Equipe that the proposals were a good starting point but there was plenty more to be discussed, including the chassis and distribution of revenues.

Ferrari chairman Sergio Marchionne said in Italy at the weekend that he agreed with Liberty on cost reduction but was opposed to anything that "distorted" the sport for commercial reasons.