Ahead of what Brown believes will be a "turbulent" period of discussions to frame F1 regulations from 2021, McLaren's executive director wants Liberty to step up its efforts to get a deal sorted.

And although Ferrari has made threats to quit F1 if it is not happy with what is offered, Brown thinks that Liberty would be wrong to appease just the sport's biggest car makers.

"I think Liberty needs to focus on what is best for the sport and what is best for the fans," said Brown, during a lunch with media at McLaren's Woking factory on Thursday.

"If that means a team or a manufacturer doesn't support that, then they need to be prepared to recognise that they are not going to make everyone happy.

"Their centering needs to be on what is best for the sport. I would rather lose one [team], replace them and have 10 teams, than have one or two teams [only] in the championship."

When asked by Motorsport.com if there was a danger that in doing that both teams could walk from F1, Brown said: "I think that is highly unlikely, but I think anything is possible. Therefore we need to land on a set of rules that allow those that are looking at the sport to be able to come in.

"In the unexpected and hopefully highly unlikely situation that they [Mercedes and Ferrari] would leave, the sport needs to go on.

"I think Ferrari is a unique case because they are Ferrari, but we have lost BMW, we have lost Toyota, and we have lost Honda before. We've all seen manufacturers come and go in the sport and it has always survived.

"So we have got to write rules moving forward about what is best for the sport, not what is best for the manufacturers."

Tough discussions

Brown has no doubts that the discussions over 2021 rules – which are likely to include a $150 million cost cap – will not be straightforward, which is why he hopes matters can get sorted by the middle of this year to avoid F1 being damaged.

"The FIA and Liberty need to move quickly so we can have as short a time of negotiations [as possible] because they will be turbulent," he said. "The longer that goes on the more disruptive it becomes.

"And also, to be fully prepared for 2021, if new engine manufacturers and teams are going to come in we know it takes a couple of years, so time is ticking.

"I would like to see us landed on what 2021 looks like by the middle of this season. Anything longer than that starts to become technically challenging."

Mercedes dominance

Brown believes the 2021 rule changes are an opportunity for F1 to improve the competitive spread, which he thinks vital because he fears as things stand that Mercedes will win the next three titles.

"Under the current regulations, current spend, you have to say they are odds on favourite to win for the next three years," he said.

"We have a chance to course correct what 2021 looks like, but we need to do that now: because I think F1 will be far more entertaining and more valuable to all of us if we have four/five or six teams winning races and that have a chance at a championship. I think that will ultimately be healthier.

"I don't think Mercedes gets any more credit winning 15 races and the championship than if they win five races and the championship. All that does [having more teams win] is make the sport more entertaining than it is today."