Daniel Ricciardo has thrown another curveball in the developing saga revolving around his expiring deal with Red Bull.

The Australian's future remains unclear beyond this season, with Ferrari and Mercedes both waiting in the wings should he decide to move away from Red Bull.

But he has sent a warning to anyone interested in signing him up not to expect a long-term agreement.

In fact, Ricciardo will insist on just a two-year deal.

The 28-year-old revealed in an interview with The Times that, due to concerns regarding the direction that the sport could potentially head towards, he is refusing to commit himself beyond 2021.

"I don't want to sign anything too long because I don't know where the sport's going," he said.

"I feel like life is happening pretty fast. Each year something might change so I don't want to tie myself down for four more years and then I'm like, 'I don't want to do this any more'.

"Ideally I'd sign a two-year contract. I think two years I can definitely be comfortable with and then see it from there. That third year will be the rule change so I will probably wait and see what happens then."

Ricciardo's statements are echoed in the situation at Mercedes, with Lewis Hamilton reportedly cautious about committing long-term with uncertainty about the direction of the sport under new owners Liberty Media.

The current engine regulations in Formula One come to an end in 2020 and negotiations between the sport's owners and the teams have been fraught with disagreements. Ferrari are among the leading dissenting voices and have suggested they could even walk away if they don't like what is on the negotiation table. 

Speculation is rife that Ricciardo could be on the move away from Red Bull with uncertainty over the futures of Kimi Raikkonen at Ferrari and Valtteri Bottas at Mercedes but the Aussie was keen to cool talk over a move.

He added: "I kind of feel like if they want me to race for them they should contact me, but they haven't.

"If we win this year then I'm staying with Red Bull. It's pretty simple. It's really just about performance at the moment."