It is not "realistic" to expect McLaren to charge for the 2021 title.

That is the admission of team boss Andreas Seidl, after world champion Lewis Hamilton said McLaren's switch to Mercedes power could make his former team an immediate frontrunner.

"It was great to see them with a good car in 2020 and maybe with our engine in 2021 they can be in the fight with us," Hamilton reportedly said.

But McLaren boss Seidl is playing down the British team's hopes.

"It's obviously good for us that Lewis respects us and watches the progress we make as a team," he is quoted by Marca newspaper.

"But as I've said before, we have a clear and realistic picture of where we are."

Seidl also said the new Mercedes deal is a "different partnership" compared to the past, when McLaren was the German giant's works partner.

"There is an official Mercedes team in Formula 1 and we are a customer, but I am very happy with everything I have seen so far and with the integration of the power unit," he said.