Mercedes Motorsport boss Toto Wolff admits the manufacturer could decide against offering engines to Red Bull Racing over a concern it could prove too good a rival to the factory effort.

Wolff has previously declared his willingness to discuss with Red Bull the prospect of an engine supply from 2017 once the Milton Keynes-based squad ends its current contract with Renault, saying it would be in the interests of the sport to ensure Red Bull remains in the sport with a competitive entry.

However, talking to Gazetta dello Sport, Wolff admits he is nervous at the prospect of supplying Mercedes' engines - considered the class of the F1 field - to a well-budgeted 'customer' team that won four consecutive world titles as recently as 2013.

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"If I wear my Mercedes Benz Motorsport hat and think about what is in the best interests of F1, then I have to say it's an interesting option.

"It would link us to a brand that has huge appeal among the young and it is a winning brand too.

"However, as the boss of a rival F1 team, it's not ideal to strengthen one of your main rivals when it knows how to make winning racing cars."

As it stands, Red Bull Racing's options beyond 2016 remain unknown, with team manager Christian Horner insisting he remains focused on its prior agreement with Renault, even though the French firm could return to F1 as a fully-fledged manufacturer entry next season too.

Should it not renew its deal with Renault, Red Bull's options remain limited to a customer supply from Mercedes and Ferrari, or from Honda, which is nonetheless known to have signed a deal with McLaren that ensures it is its priority partner.

Red Bull Racing has previously ruled out the prospect of developing its own engine, while the struggles of Honda are believed to have deterred potential new entrants.