That is the claim of Dr Helmut Marko, the boss of the energy drink company's driver programme.
But Marko told Germany's Sport Bild that Red Bull is in charge.
"Ricciardo and Verstappen have fixed contracts," he said. "Ricciardo for 2018, and Verstappen with some clauses for even much longer."
And the Austrian said Red Bull is not willing to let any of them go.
"That also applies to Carlos Sainz," said Marko. "He is also bound to us in the longer team. Until 2019.
"Only we can end contracts -- the drivers cannot."
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