Red Bull team principal Christian Horner insists everyone within his organisation is relishing the biggest challenge they have faced for many years.

After winning four successive drivers' and constructors' titles, Red Bull now find themselves in the unaccustomed role of hunting down one of their rivals in this year's championship battle.

Red Bull, however, would appear to face a mountainous task if they are to continue their winning run in light of Mercedes' astonishing start to the new campaign.

Five consecutive victories, and notably four straight one-twos, have propelled Mercedes into a 113-point lead over the Milton Keynes-based team.

As for reigning four-times champion Sebastian Vettel and team-mate Daniel Ricciardo, the duo currently trail Lewis Hamilton by 55 and 61 points respectively in the drivers' standings.

Ahead of this weekend's Monaco Grand Prix, won by Nico Rosberg from pole position last year, Mercedes are hot favourites to again take the chequered flag at the principality.

Horner appreciates the size of the task at hand, but maintains no-one within his team is yet giving up without a fight.

"Mercedes have got themselves into a very strong position, but nobody is unbeatable," said Horner.

"We have a great team, great strength in depth, and everybody is up for the challenge.

"It is a probably a bigger one than we would have liked, but everyone is up for it.

"It has really motivated the team, galvanised them and said, 'Okay, we have something to chase'.

"It is the difference from being the hunted to the hunter. There is a real sense of determination in the team to close this gap down."

Horner insists they are not looking for any favours by hoping Rosberg and Hamilton trip over one another on occasion.

"Nobody wants that," added Horner.

"If we want to close the gap on track we will do it in a racing way. We want to try to beat them, and beat them fair and square."

To do that, however, Red Bull need some assistance from power unit supplier Renault as the car lacks outright speed in comparison to the Mercedes.

"We know we have a very good chassis, we can see that," said Horner.

"It is a matter of working with Renault to get the most out of the engine because at the end of the day the car has to work as a package.

"So we are supporting as much as we can to ensure the engine moves closer to Mercedes."