Ferrari threatened to walk away from F1 in 2020 when it saw the first blueprint for the set of engine regulations, tabled last October. Negotiations between F1 owners Liberty Media and the 10 teams which make up the grid have continued since, with a set of proposals being presented ahead of the Bahrain Grand Prix earlier this month.

Team boss Maurizio Arrivabene was tight-lipped about Ferrari's reaction to the proposal, which was broadly outlined to the public in a five-point plan. His chairman has refused to back down from the threat this week.

"If F1 becomes more of a spectacle than a sport, if we go in the direction of NASCAR races, then Ferrari will leave," he said at a shareholders' meeting, reported by AFP. "If there are any proposals that distort F1, I think Ferrari will pull out."

Mercedes boss Toto Wolff, who has warned F1 to take Marchionne's statements seriously, called the Liberty proposal a "starting point of dialogue" but said many of the finer details needed clarifying. Marchionne says it is those details which will ultimately influence Ferrari's long-term decision.

"We are working with Liberty Media to find acceptable solutions. We had a proposal from Liberty 10 days ago, we expect to know the details and then we will make choices in the interest of Ferrari. We could look for alternative solutions, it's not a threat, but it does not mean we stop shopping."