Daniel Ricciardo hopes to win a championship with Red Bull but says he may depart if they cannot provide him with a competitive drive.
The Australian was promoted from sister team Toro Rosso in 2014 and has won five grands prix during his time with Red Bull.
The 28-year-old is out of contract at the end of the 2018 season and is aware his next move could well be crucial in his hopes to win a drivers' title.
Red Bull have failed to compete with Mercedes and Ferrari in recent seasons, having dominated before the turbo-hybrid era, and Ricciardo admits he is growing impatient.
Ricciardo has now warned his team that he could walk away when his contract expires if they cannot make significant improvements in 2018, as he is desperate to pick up a title before his career comes to an end.
"I went through that impatient phase for sure, and I am still bordering that - because I don't want to leave F1 without a championship," he told Autosport at an event promoting his Ricciardo Kart venture.
"At least right now, I still believe I can do that, absolutely. I am looking for it - sooner rather than later.
"I thought we would be in with a really good shot this year, but it hasn't turned out like that. It really needs to happen with Red Bull next year - at least from my point of view.
"I've been here for quite a few years now and I think next year we need to make a bigger step next year than we did this year, to really convince me that I can win with them."
He added: "I have got decisions to make once my Red Bull contract is up. It is the first time in my professional career that I've been a free agent.
"I've been with Red Bull since the start and it has been awesome. But it is up to them as well if they would want to continue, and then it is a decision where I think it will be best."
Ferrari could have a seat available at the end of 2018 as Kimi Raikkonen is due to fall out of contract, Lewis Hamilton's Mercedes deal also ends at the same time as Ricciardo's Red Bull contract and fellow Silver Arrows driver Valtteri Bottas is out of contract at the end of this season.
