Melbourne - Red Bull and Mercedes have stated that they are against more teams being added to the Formula One grid after the sport's chief suggested 12 would be better than the current 10.
FIA president Jean Todt has admitted he is keen to boost the number of teams, but is facing resistance from constructors who have witnessed several outfits come and go as they struggle with spiralling costs.
"I always go for quality over quantity. I think we've got 10 teams that are in pretty decent health at the moment, compared to previous years," Red Bull chief Christian Horner said.
"As we see when the grid has expanded (in the past), none of those teams that came in a few years ago are still here.
"In Formula One the cost of entry is so high it's virtually impossible unless you are a multi-multi billionaire, and sometimes even that's not enough," he added.
"So I think we have a good balance at the moment and I prefer that we look after what we've got and have good quality and closer grids than inviting more entries for the sake of filling the grid."
Todt was quoted by Sky Sports this month as saying he wanted to add two more teams, although he described it as a "long debate".
"As you know we are talking together with the commercial rights holder (Liberty Media), with the teams, about the renewal of the Concorde Agreement (beyond) 2020. And we are considering a lot of things," he said.
"Of course, for me, I think it would be better to have 12 teams. If you speak about that to the actual team principals, they are not very happy about that because of course it will change financial distribution, so it will be different for them."
In recent years a number of teams have entered the sport but not survived, including Force India, HRT, Caterham and Marussia.
Mercedes team chief Toto Wolff said it had to make sense financially before any new teams were considered.
"I think we are in a decent place right now," he said. "For Formula One and the value of the teams, it is more important to keep those franchises limited to attract the best brands."