Lewis Hamilton drives his Mercedes at last weekend’s United States Grand Prix in Austin, Texas.

Mercedes motorsport boss Toto Wolff is beginning to thaw with regard to his stance over an unfreezing of the engine rules.

The manufacturers of the power units – with the engine one of the six components that comprise the system – have been embroiled in a row for several weeks now over future plans on engine development.

Given their domination this year since the introduction of the 1.6-litre V6 turbo-charged units, Mercedes have made it clear they will not allow a change in the rules that would allow open development on the engine.

Rivals Renault and Ferrari, who have struggled in contrast, believe as the technology being used is still in its infancy they should be allowed the opportunity to improve their systems.

Mercedes have been offered a compromise solution whereby development takes place into next year, but beyond that the door closes.

The downside is the cost implications, particularly at a time when finances are on the agenda with Caterham and Marussia recently entering into administration.

That resulted in a threatened boycott of the race in the US on Sunday, but with a solution on the table for commercial rights holders, CVC Capital Partners, to mull over ahead of this weekend’s penultimate race of the campaign in Sao Paolo.

Addressing the issue, Wolff said: “We think opening up the current regulations is nonsense.

“When you look at the rules eight per cent of the engine only is frozen for next year, so you can change 92 per cent. So we can never speak about anything such as a freeze.

“What the other power-unit suppliers say is that needing to develop the power unit until the 28th of February is a problem.

“They’re asking whether it is possible to extend that period and bring another homologation (of the engine) later in the year, probably with a larger scope of developments.

“That means you have a second spec, so you have to do all the dyno running for a second engine that would be introduced.

“You cannot track test it because you are allowed to use one-spec of engine only, so you have to do all the dyno running and make – in our case – eight powerful and reliable engines.

“This is going to cost a fortune.

“But if this is the compromise needed to guarantee long-term stability and agree long term we are not going to change the rules every year, that is something we will look at.

“What we have said is we are calculating that as we are a team which needs to deliver eight power units at a time (Mercedes have three customers), Honda two, Ferrari and Renault four.

“There’s a big difference, so once we have gathered all the data over the next couple of days we’re going to do that in Sao Paolo.”