The Sugababes are among the bands whose music is being offered

As part of the deal, AT&T will offer its subscribers Napster tracks for $1.99 each (97 pence) or $7.49 for five songs a month from mid-November.

The firm already offers downloads from independent labels through eMusic.com.

AT&T has not said which phones will work with the service, but they will not include Apple's iPhone.

AT&T has North America's largest wireless network and has an exclusive deal for the iPhone in the US.

However, it cannot offer Napster to users of the iPhone, which can only access songs from Apple's iTunes music store.

AT&T also said it aimed to offer music downloads exclusively to mobile phones through direct deals with artists.

Mobile phone operators have been clamouring to offer services, such as music and video downloads, to boost their revenue streams.