The first three teams have signed up for the 2021-2025 Concorde Agreement - but one of them is not Mercedes.

Ferrari, McLaren and Williams are the first to announce that they have officially agreed to Liberty Media's proposed new regime.

Prior to last weekend's Spanish GP, Toto Wolff had indicated that Mercedes is not ready to sign - and scolded those who insisted they were.

But in Barcelona, he said he would indeed sign up the German team - having publicly slammed some of his rivals for being "up the a**" of the sport's owners.

"What frustrated me was that we, as the teams, are not capable of really joining up to have a common standpoint," Wolff explained.

"We have these meetings and everybody seems to be interested in the same clarifications for the contracts, and then we leave the meetings and on air I hear opinions that differ very much to what was said within the meeting.

"For me, I have come to a point that if we're not capable as teams to have a joint standpoint for the benefit of the teams, then we'll have to go back and have our own," said Wolff.