YouTube will soon give viewers the option of paying a monthly fee to skip ads.

On Wednesday, the online video service sent a letter to its most-popular content creators asking them to sign off on new contract terms to allow for the change.

It's not clear when the option will be offered or how much the fee will be.

A YouTube spokeswoman declined to confirm specifics but said in a statement, "giving fans more choice to enjoy the content they love and creators more opportunity to earn revenue are always amongst our top priorities."

The streaming video service owned by Google Inc. first offered pay channels in May 2013 and also launched a paid subscription, ad-free music service called Music Key to select participants in November.

The moves are all part of a strategy to diversify its revenues, although advertising remains its core. At a media conference in October, YouTube CEO Susan Wojcicki said ad-free subscriptions represent an "interesting model" and that the service was exploring how to give its users options.