Toro Rosso insists technical director James Key's planned move to McLaren is not being undertaken with its consent by confirming that the Englishman still has a long-term contract with the team.
McLaren announced on Thursday that Key will be joining the Woking outfit, although the didn't provide details of either his job title or, crucially, the timing of his move.
Toro Rosso in return has opted to make it clear that Key is still under contract.
It is believed that there are still negotiations to be concluded with McLaren in relation to Key's release, and that going public to remind the world of its contractual claim on him is simply part of Toro Rosso's strategy.
Some observers have suggested that Toro Rosso harbours hopes of using the situation to land the services of McLaren junior driver Lando Norris for 2019 and beyond, but it seems unlikely that a settlement between the two teams would be anything but financial.
Key was understood to still be working at Toro Rosso's factory in Faenza today.
It's not yet clear whether he is destined for gardening leave, which is the usual course of action in such cases, especially given that his situation is now public.
"James has a valid long-term contract with Toro Rosso," Tost told Motorsport.com. "And that's all what I can say about this. There's nothing more to say."
Asked if the team was in negotiations with McLaren about the terms of his departure, he said: "I think they will come to us. We will see, or not.
"I have no reason to discuss it with them, because we have a contract. Everything has been said."
Tost did however insist that the team has enough strength in depth for the uncertainty over Key's future to not have an impact on its immediate development plans
"Of course, it's not supporting us, all this story around James. This is clear. But I think the team from the technical side is strong enough, and there's a good view about what we have to do with it all.
"But we simply need also the time. I hope that we will bring some upgrades in the second half of the season, and if they are working as expected, I hope we can close the gap once more."