Esteban Ocon and Robert Kubica look to be tussling with incumbent Sergey Sirotkin for the second race seat at Williams for 2019.
We reported this week that Kubica has secured $10 million in backing by a Polish oil company that puts him in the running for the promotion from reserve driver.
But Williams boss Claire Williams said in Austin that Ocon, the talented Frenchman who is losing his seat at Force India, is a top contender.
"Having someone with Esteban's talent, if only for one season, is something I'm open to," France's Auto Hebdo quotes her as saying.
Like Ocon, Williams' confirmed driver for 2019, rookie George Russell, is a leading member of Mercedes' driver programme.
"We signed George because we could sign an agreement for several seasons that allows us to build for the future," Williams added.
"We have been working hard for six months to ensure that our 2019 budget allows us to hire drivers on merit.
"For the second seat we do not have the same room to manoeuvre. We would like to proceed as we did for the first driver but the road to get there is harder.
"We are working hard to ensure that Esteban stays in F1 next year by coming to us. We are doing everything we can to get there," Williams added.
Ocon admitted he hopes his Mercedes connections help give him a boost for the seat at Williams.
"I think it's a good thing that Mercedes has managed to place one driver because it's been a little difficult for me and Pascal (Wehrlein)," he said in Austin.
"There is still the other seat so we'll see what happens. There are still discussions," Ocon added.
He said he does not feel pushed down the Mercedes pecking order just because Russell was signed up ahead of him.
"He has signed for several years and that was not our intention," said Ocon. "He is at a different point to me in his career and I don't see it that he stole my place."