Brendon Hartley says the uncertainty about his place at Toro Rosso for 2019 is getting "annoying".
It is believed team owner Red Bull will replace the New Zealander with rookie Alexander Albon.
"We have not yet made a decision," Dr Helmut Marko told motorsport-magazin.com. "Important decisions take time."
Hartley has generally underperformed in 2019 but he says he has upped his game more recently.
"I’m happy with my races but it’s getting more and more annoying to answer questions about my future every week," he is quoted by Speed Week.
"I read that I have to beat my teammate to prove myself, but I was ahead of Pierre in Singapore before the team order, and ahead of him again in Russia before my car broke down.
"I was also faster in qualifying in Suzuka and also here in Austin I was ahead. Let’s see what happens," Hartley added.