Horner: We have good alternatives for Ricciardo

Horner told CNN Sport, "Daniel's contract expires at the end of this season and our intention is to have him with us in the future."

"The plan is to continue with the line-up that we have now, but if that isn't possible, we have other good alternatives."

"We have good drivers in the junior program and, in addition, we still have Carlos Sainz under contract, although he is now with Renault."

One option for Ricciardo is to replace Kimi Raikkonen at Ferrari from next year, but the jury is out on how Sebastian Vettel would welcome his former Red Bull teammate to Maranello.

Ricciardo emphatically beat Vettel when they were teammates at Red Bull in 2014, the German at the time off a four successive F1 world title winning streak and the Aussie just promoted from Toro Rosso.

The Mercedes option is one that has bubbled in the paddock since Bottas was handed another single year deal. In the past, Ricciardo has made it clear that he would relish partnering Lewis Hamilton and believes he could beat the Briton with equal equipment.

But Horner appears to have all bases covered, "We still have good options, as Lewis [Hamilton]'s contract also expires. It's hard to see him leaving Mercedes, but we never say never."

As for Red Bull's title hopes, Horner predicted, "Mercedes are surely going to be the favourites, because they have been very strong and have dominated during the last years."

"The regulations are very stable, so we hope to reduce the gap, especially in circuits where we can be more competitive. Our challenge is to be in the fight for victory against Ferrari and Mercedes," added Horner.