Mercedes needs to 'back a horse' - Horner

Valtteri Bottas's two grand prix wins over the first half of the season have kept him within striking distance of Mercedes team-mate Lewis Hamilton and world championship leader Sebastian Vettel.

But while Vettel's title bid appears to have the full support of Ferrari, with Kimi Raikkonen seemingly not in contention, Mercedes is supporting both of its drivers equally, evidenced by Hamilton letting Bottas through for third place in the Hungarian GP after the Finn had moved aside earlier to attack the Ferraris.

Horner believes that approach cannot last, and he expects Hamilton to be the driver that will take the fight to Vettel.

"The dilemma that Mercedes have got is that Hamilton is their lead driver and at some point you have to back a horse," said Horner.

"Ultimately it will probably come down to those two guys [Hamilton and Vettel], and Ferrari's position with Kimi was far clearer."

Horner added that he was impressed with Hamilton's commitment to giving the place back to Bottas, despite the fact the second Mercedes had fallen nearly eight seconds adrift by the start of the final lap.

Asked if he was surprised Mercedes swapped places at the end, Horner said: "On the one hand yes, but on the other hand, it would have been harsh on Valtteri, because you are effectively telling him you are out of the championship the moment you did that.

"I was impressed Lewis gave it back, because you are just giving away more points to your biggest rival.

"We did it in Monaco two years ago [with Daniil Kvyat and Daniel Ricciardo] but it is slightly different when you haven't got a driver competing for the world championship."

Leading drivers' standings