Alex Albon looks set to keep his seat at Red Bull, even though Dr Helmut Marko says he is in "no rush whatsoever" to make a final decision.
The other two candidates are Pierre Gasly and Daniil Kvyat, the current Toro Rosso drivers who were both previously ousted from Red Bull Racing.
'I'm totally focused on my job here'
"Gasly is doing well now," Marko, who demoted the Frenchman earlier in 2019, told Sky Italia.
Gasly also commented in Austin: "I have not forgotten how to drive, and I drive exactly the same as I did before.
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"But I am not thinking about Red Bull Racing. I'm totally focused on my job here."
Russian Kvyat, meanwhile, said he is happy to have heard Marko's recent statement that he is a contender to be Max Verstappen's 2020 teammate.
"Yes, it's great to know that, but I don't follow the story especially closely. I am focused on my work, and when Red Bull makes a decision, whatever it is, I will accept it respectfully," he said.
The British-born Thai rookie Albon appears poised to retain the plum seat.
"Albon gets better with each race. He works incredibly hard and keeps both feet on the ground," Marko told Auto Motor und Sport.