Carlos Sainz has said that he does not want to be a back-up Red Bull driver for the rest of his career.
The Spaniard had eyed a move from Toro Rosso to the senior team, and was then shortlisted by the works Renault team for 2017.
Yet Red Bull is keeping him at Toro Rosso, not only to lead the Faenza team but also to be ready to step up should he be needed at short notice.
"To my regret, Red Bull Racing are very happy with their drivers," he said in Austin.
"It's good for them that there is a third driver who is waiting for the right moment, but I can't wait my whole life. I hope they understand that."
He said that he is happy to stay at Toro Rosso for 2017, but after that is keen to "move on".
Asked if he thinks that Red Bull will again intervene for 2018, Sainz said: "I hope not. Red Bull are tough but also fair.
"If they do not need to replace one of the drivers, then I'm sure they'll find a fair solution."
Sainz has picked up 30 points in the 2016 championship.
