The new online service will enable subscribers of XM’s radio service to download and buy digital songs from Napster’s playlist.

The companies are planning to launch the XM + Napster service in the fourth quarter of 2005, to coincide with the release of the new XM/MP3 players which XM has developed with electronics giant Samsung.

Once the MP3 player is connected to a PC, the new service will match the marked XM titles with songs in Napster’s catalog to enable XM subscribers to download and buy the tracks.

Subscribers can also use the XM + Napster service to organize playlists and transfer them to XM’s MyFi portable radio, which is currently retailed at $299. Subscribers without the new MP3 devices can tag songs and buy them online through XM Radio’s web-based service.

XM subscribers can pay a monthly subscription fee for unlimited Napster tracks or they can purchase individual songs.

The move represents XM’s first attempt to integrate its subscription radio service with the popular MP3 market.