AP Photo: Andy Wong.

London - Daniel Ricciardo says he does not want his next Formula One contract to tie him down for the next four years due to the uncertainty over the sport's future and instead wants to sign a two-year deal.

The 28-year-old Australian, winner in China at the weekend and one of the hottest properties on the market, is out of contract with Red Bull at the end of the year.

"I don't want to sign anything too long because I don't know where the sport's going," The Times newspaper quoted him as saying on Wednesday.

"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," he added. "That third year will be the rule change so I will probably wait and see what happens then."

Formula One's current engine regulations last only to the end of 2020, when team agreements also expire, and the sport is deciding how the future should look and what kind of engines will be used.

Ferrari has already warned that it could walk away if it does not like what's on offer.

Red Bull could have a new engine partner as early as next season, with the team weighing up whether to stay with Renault or switch to the improving Honda units used by their Toro Rosso team.

Mercedes has yet to announce a new deal for four times world champion Lewis Hamilton, who is also out of contract at the end of this season and has said he wants to see what the future holds before committing.

While Ferrari's Sebastian Vettel and Red Bull's Max Verstappen have long-term deals, there is uncertainty about the futures of Kimi Raikkonen at Ferrari and Valtteri Bottas at Mercedes.

No word from Mercedes or Ferrari

Ricciardo would be a strong replacement for either but the Australian told the newspaper that neither team had been in touch so far.

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

Ricciardo has said consistently since last year that he just wants to be in the fastest car and would be happy to stay at Red Bull if the team can provide it.

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