Formula 1 could move to three-car teams if Red Bull decide to pull out of the sport, according to Mercedes motorsport boss Toto Wolff.
Red Bull are shopping around for a new power unit supplier as their relationship with Renault is coming to a messy end once the 2015 season is up and they are in talks with Ferrari.
However, they have made it clear that they, along with sister squad Toro Rosso, will quit the sport if Ferrari can't guarantee them parity with the works outfit.
That would leave nine teams on the grid in 2016 as the new American-based Haas F1 Team are set to join, but Wolff has revealed they do have other options.
"Yes, if a team would leave – and we had this discussion about Lotus a while ago – third cars are a solution to fill up the grid," he said. "For me personally it is a pretty exciting idea.
"I'd rather have Red Bull in the sport than third cars and a grid of 27 or 28 cars. But this is definitely one of the fall-back solutions."
It was initially suggested that Mercedes could supply Red Bull with engines next year, but the German company decided against it, and Wolff insists they won't change their mind.
"You can't close your eyes to the fact that this [F1] is a platform and it needs players and it needs a competitive environment and it needs competitive teams," he said.
"That was part of our consideration. Red Bull is a hip brand and it's good for Formula One that Red Bull is in here, but it is also an environment where you need to look at yourselves and the team's performance with the priority.
"When it comes up to the decision, would you rather go with the platform and the good sport or would you rather go with the team's perspective. It's clear from our point of view that you need to prioritise your own competitiveness.
"We have waited so long to have success with our own works team ever since Mercedes decided to go into Formula One and not continue only as an engine supplier. Obviously this had a rationale and that rationale is still valid today and this is why we took the decision some weeks ago not to continue [negotiations with Red Bull] and then Ferrari picked that ball up."