Teams are not committed yet as no new Concorde Agreement has been signed, and F1's new management has made it clear that those who had preferential deals under Bernie Ecclestone – including Red Bull – will have to accept a level playing field, with payments based on performance.

Red Bull is also concerned about budget caps, as it is the only one of the top three teams not linked to a car manufacturer and engine supply, and it has doubts about how equitable any restrictions could be.

Horner acknowledged that Red Bull boss Dietrich Mateschitz could pull the plug if he's not happy with the shape of F1 in 2021.

"Absolutely," Horner told Motorsport.com. "And that's his right.

"He's passionate about motorsport, he's passionate about F1, he's enthusiastic about the new engine partnership with Honda and the potential that brings, but of course F1 has to deliver for the Red Bull brand as well.

"It needs to be exciting, it needs to be cost effective, the racing's got to be great, and we need to be able to play on an equal and level playing field with OEM and manufacturer teams.

"I think like all of us he's waiting to see what is F1 post-2020."

Horner said a flying start to the Honda partnership would not be essential to maintaining Mateschitz's motivation.

"He's never lacked motivation. Through good days and bad days he's always been tremendously supportive, and invested probably more into F1 than any other entity.

"Two F1 teams, a grand prix, plus all the promotion that Red Bull does around the world supporting F1, it's enormous. He wouldn't do that if he didn't believe in the sport."

Ecclestone believes that while there is no Concorde, there remains a risk that teams or manufacturers could pull out of the sport.

"The longer they leave it, the more chance there is of some of the teams stopping," the former F1 boss told Motorsport.com.

"Maybe Mercedes will be stuck into Formula E, because they think Formula E is more in line with the way the car industry is going to go.

"Red Bull don't need to be in it. They get so much publicity from all the other things they do. For them if they stopped it's not going to damage them at all.

"People think Ferrari would never stop, but the Ferrari brand is so, so strong it would be difficult to damage Ferrari. They could easily do something else in motorsport.

"The longer they leave it, the worse it is for everyone – it's worse for the teams, worse for Liberty.

"From what I understand, nobody has said the most important thing, which is this is what we want to pay you guys. We'd like a much better show, and we're prepare to pay you this.

"I think if I was a shareholder I'd be happier once all that got put to bed. Five years, everyone's happy, the teams are happy, the promoters are happy, and get on with it."