Toro Rosso looks to have made its decision about Daniil Kvyat's teammate for 2019.
It appears it will be rookie Alexander Albon, a Briton with Thai heritage who raced in Formula 2 but recently signed a long-term Formula E contract with Nissan.
Formula Spy reports that Red Bull has managed to negotiate an end to Albon's Nissan deal.
"Alex called me and then Helmut Marko called me from Japan and I knew that as the process was starting we had to go ahead and find a solution," said Nissan boss Jean-Paul Driot.
He said the Japanese manufacturer was "quite reasonable" about not standing in Albon's way.
"When you have a 22-year-old driver who has an opportunity to go to F1 we all know what it is for them, it's their life," said Driot.
"We know we could battle with the contract, because we have a contract, it's quite clear. But you cannot compromise the career of a young guy."
However, in Austin, Red Bull team boss Christian Horner denied that a Toro Rosso deal for Albon is now set in stone.
"There's nothing fixed. Nothing other than speculation at the moment," he said.