Liberty Media is now mere days from revealing the 2021 engine rules to the Formula 1 teams.

Despite that October 31 presentation date, there remains plenty of uncertainty in the paddock about what those regulations will actually be.

"Normally it's pretty well leaked," Force India boss Bob Fernley told Auto Motor und Sport, "but this time it's different.

"We know a little but not much. The new owners are keeping their cards face down."

What is known is that the 2021 engine will be based on the current 1.6 litre V6s and will definitely include an MGU-K.

However, it is unclear if the MGU-H will still be in place, and whether there will be a single, larger or even twin turbo.

Mercedes's Toto Wolff said: "If we omit the MGU-H, we lose 60 per cent of the electrical energy. How will we get that back?"

Red Bull, however, argue that axing the complex MGU-H will mean that independent suppliers like Ilmor and Cosworth can seriously consider entering F1.

"With MGU-H, we will not have those companies, and we definitely want them in the boat," said Dr Helmut Marko.

Whatever is presented early next week could be highly controversial, particularly as Liberty does not need the teams' approval for 2021 due to the expiring Concorde Agreement.

Mercedes's Niki Lauda said: "There is no point in being political now.

"They have decided something, they will tell us, we will listen, and then we will decide if it's good for us or not."

The current championship continues on Sunday with the Mexican Grand Prix.