SEATTLE — RealNetworks Inc. is teaming up with SanDisk Corp. to release a portable music player that more closely links with RealNetworks’ Rhapsody online music service, in the latest attempt to take on Apple’s iPod and iTunes stronghold.

Analysts see the deal, to be announced Monday, as a way for SanDisk and RealNetworks to join forces against a new common foe: Microsoft Corp., which recently announced plans to release its own Zune portable music player and service.

Redmond-based Microsoft has been providing the technology that allowed services such as Rhapsody to transfer songs to portable music players without compromising the digital rights of that content. But many say they think Microsoft’s plans to release the Zune service and a player made by Toshiba Corp. could make the software giant a significant competitor.

“This is kind of a way for both Rhapsody and SanDisk to say, ‘Well, if you’re going to compete with (us), guess what, we’re going to compete with you,’ ” said analyst Phil Leigh with Inside Digital Media.

Katy Gentes, a product manager for Microsoft’s Zune effort, said Friday that the company remains committed to the Windows Media platform it provides to partners and will continue to invest in it.

Under the deal, RealNetworks and SanDisk plan to release the Sansa Rhapsody, a portable music player based on SanDisk’s e200. The companies said they expected the gadget to be available in time for the holidays, but they would not say exactly how much it will cost.