Although critics have largely downplayed the iPod-killing potential of Microsoft's Zune player and digital store, the Seattle software giant has struck a landmark deal with Universal Music that could cause Apple some grief down the road.

Zune, in three colors.

Microsoft said late last week that it had signed a deal with Universal, the world's largest record company, to share a percentage of the sales from its Zune portable music player, which hits stores tomorrow, in order to license songs for Microsoft's digital music store, which launches next week. The deal is the first of its kind between a record company and a digital music seller.

The revenue-sharing deal is on top of the industry-wide standard fees Microsoft will pay Universal to license the label giant's music, which includes U2 and Jay-Z, for its Zune MarketPlace digital store. Microsoft called the deal a "ground-breaking" royalty arrangement. Financial terms of the deal weren't disclosed.

"This move demonstrates there can be a win-win situation," UMG Chairman Doug Morris said in a statement.

If other labels follow Universal in seeking revenue-sharing deals with Zune, the move could complicate matters for Apple when it renegotiates its own licensing deals with the labels next year. Apple has built a more than 75 percent market share in both MP3 player sales and digital music sales, and has used that dominance for leverage in negotiating label deals.

"It shows that part of the Zune strategy isn't only to win the hearts and minds of consumers but the hearts and minds of record companies as well," Michael Gartenberg, research director at Jupiter Research, told Reuters. "This is a way for Microsoft to drive a wedge between labels and Apple, but it doesn't give music companies leverage against Apple until Zune gets market share."

The Zune player makes its much-hyped debut tomorrow. As previously reported, the 30GB device will sell for $249, the same price as the 30GB iPod. It comes with an FM radio, a large three-inch display screen, and restricted, Wi-Fi-based music sharing between Zune users.