Red Bull have slapped down "disingenuous" Carlos Sainz after the Spanish Formula One driver suggested he was likely to leave their Toro Rosso team at the end of the season.

"We've taken the option on Carlos Sainz and he will be in a Toro Rosso next year," Red Bull team principal Christian Horner told Sky Sports television during practice for the Austrian Grand Prix on Friday.

"It makes no sense loaning him out. I don't know where he thinks he'll be.

"It's a bit disingenuous saying stuff like that. Without Red Bull he wouldn't be in Formula One."

Sainz had told reporters on Thursday that he was unlikely to stay at the Red Bull-owned team for a fourth season and was open to offers.

The 22-year-old, who has eclipsed Russian team mate Daniil Kvyat this season, is seen as a rising star and has been linked in media speculation to a number of other teams.

His chances of moving up to Red Bull next year look non-existent, however, with the former champions having Australian Daniel Ricciardo and Dutch teenager Max Verstappen locked in.

"Our plans for next year is that our cars will have the same numbers on them next year," Horner said. "Both drivers will be with us 100 percent."

Toro Rosso, established as a feeder team for Red Bull, has a history of moving young drivers either upwards or out. Those who have graduated include four-times world champion Sebastian Vettel and their current race winners.

Others have been less fortunate, their Formula One careers effectively ended after being cast out of the Red Bull fold.

Kvyat is in the rare position of having been promoted and then demoted again in a swap with Verstappen, who won in Spain on his Red Bull debut last year.