Toro Rosso: F1 calendar mustn't go below 20 races

F1, which firmed up a 21-race schedule for 2019 on Thursday, is considering new races in Miami and Vietnam going forward, despite concerns over the size of the calendar.

Earlier this season Renault F1 chief Cyril Abiteboul told Motorsport.com he thought the schedule had expanded too much and needed an aggressive cut, possibly to as few as 15 or 16 races.

Asked by Motorsport.com about that suggestion, Tost said: "I think it's not the number of races or the size, it's the show which we offer and the level of the entertainment.

"If you have 15 boring races people will not watch any more. No, I think we should have around 20, 22 races and I think this is a good number.

"We also should not forget that we are a global player and therefore we need a certain number of races to stay a global player.

"I would absolutely refuse to go below 20 races. The year has 52 weeks, therefore we have a lot of time."

Red Bull team principal Christian Horner and Sauber boss Frederic Vasseur said 21 races is the maximum that is reasonable.

"At one stage also we are losing the exceptional [nature] of the event," said Vasseur.

"The more races you are doing, everybody is used to and at one stage we have to keep the exceptional side of the races.

"For me it's a bit too much but I will follow the calendar. I won't stop after 18 next year."

F1 has axed its unpopular triple-header for 2019 but may reintroduce it because of the challenge of packing so many races between March and December.

Vasseur suggested that between 18 and 20 races would work better, while Horner described a 21-race calendar as reaching "saturation point".

However, Horner said Abiteboul's suggestion of 15 or 16 races was too low and, referring to F1's rules limiting the number of engines allowed per season, joked that "maybe Cyril was looking at grid penalties or something".

"There's only so many chapters you can have in a book and I think at some point you go beyond what's relevant," he said.

"I think to go as low as 15 or 16 I think is too low –– but I think that 21 is the upper end.

"It's tough for the guys in the garage, for the travelling staff, it's tough for everybody involved.

"The really encouraging thing is that there are some great venues that want to host Formula 1 races and events and I think that that should provide natural competition for the venues that are already on the calendar."