Red Bull team principal Christian Horner believes this year's driver market will be dictated by Sebastian Vettel's next move.

Several top drivers are out of contract at the end of this season, including Vettel, his Ferrari teammate Kimi Raikkonen, McLaren's Fernando Alonso and Mercedes' Valtteri Bottas.

Ferrari has left the door open for Vettel to remain at Maranello, but with Toto Wolff yet to confirm Bottas for 2018 there are still rumours he could make a switch to Mercedes.

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Horner believes the rest of the available drivers will fit around Vettel's plans, but made clear that Red Bull's line-up of Max Verstappen and Daniel Ricciardo would remain unchanged.

"I guess Sebastian probably holds the key to the driver market at the moment," Horner said. "But certainly within Red Bull Racing there will be no changes to the driver line up."

Horner said this week that Toro Rosso driver Carlos Sainz could be bought out of his Red Bull contract at the right price, but stressed the same does not apply to Ricciardo and Verstappen for 2018.

"They are totally locked in and there is no price that would be high enough for those two," he said.

Ricciardo will be out of contract in 2019 and Horner said his team would enter talks to keep the Australian at Red Bull closer to the time.

"2019 is still a long way away. Daniel is out of contract. He will have completed the fifth year of his contract with us, and I am sure we will start the talks with Daniel a little bit closer to the time for '19 an onwards."