McLaren believes there is no reason to delay the switch to Mercedes engines in 2021 even if won't be the "most efficient".

The two sides had planned to coincide the reforming of their historic partnership with all-new cars that were originally scheduled to be introduced next year.

However, amid the ongoing coronavirus pandemic, it was decided to postpone them for one year at least, meaning McLaren will have to integrate the Mercedes unit into their current MCL35 while also abiding by agreed limits on car development. 

"For sure, there will be restrictions in terms of how good we can integrate this power unit into the current car," F1 team boss Andreas Seidl said.

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"We have a great relationship with the FIA, they will monitor very closely that we are only allowed to do the changes that are absolutely necessary to install the Mercedes power unit.

"They will monitor closely that we don't touch any of the areas in the surroundings of the power unit that will give us, let's say, additional performance gains, which we fully understand and agree to.

"In the end, we need to look at the bigger picture, which is we need to agree - and we also support - this freezing [of the rules] that is happening at the moment because that ensures maximum cost-saving for this year."

The McLaren chief also defended the decision to push ahead with the Mercedes switch, adding: "I don't think it can be done in the most efficient way because there are some restrictions.

"Why we're doing the switch? We have contracts in place, and there is no reason why we don't continue with that plan."

There is also the possibility that McLaren could use two different engines in 2021 if the current season extends into January as has been suggested.

"If that happens, that we are going racing in January, I don't think there will be any issue regarding our agreement we have with Renault," Seidl prophesied.

"It's important to state we have a great relationship there, an open and transparent relationship, so I don't see any issue."