The Milton Keynes-based outfit is locked in a tight fight with Mercedes for the F1 title, with the squads having taken one victory apiece so far.
Mercedes has been clear, however, that it feels it is playing catch-up in speed terms, and is now the hunter in F1 rather than the hunted.
Speaking earlier this month, team boss Toto Wolff said: "It's theirs to lose, ours to win, because when you have the quickest car, you have got to deliver on that."
But Horner has scoffed such suggestions, and believes that Mercedes boss Toto Wolff is so eager to big up Red Bull's prospects only as part of a psychological game between the two teams.
"Of course, it's used to try to put expectation and to try to create pressure," Horner told Motorsport.com, when asked about the 'favourite' tag that neither t