Ericsson and Napster have developed a music downloading system that operators can use to deliver full songs to their customers' mobile phones.

Users will be able to pay for the music service on their phone bills. Although pricing has not yet been decided, the companies will use Napster's current pricing model as a starting point.

Napster boasts over 1m song titles, according to its website. Today, these can be downloaded to PCs over fixed-line Internet connections for a basic subscription fee of £9.99 or 79p a song.

The companies said the mobile phone service will begin within a year.

The deal highlights how popular music downloads have become, fuelled by better digital music quality and the ability to store ever greater amounts of songs, pictures and other data on increasingly smaller devices. The popularity of using music for mobile phone ring tones has also helped spur the trend.

The Napster-Ericsson music system will be sold to mobile service providers, who will then resell the service to their customers. It is designed to work with mobile phones already on the market and new ones designed for high-speed networks.

But the service will face stiff competition from companies already up and running with similar music stores.

Nokia announced similar plans to offer a service to carriers in February, working with Microsoft and online music catalogue Loudeye.

In addition Orange announced earlier this week it had teamed up with local subsidiaries of Nokia and HP to soon begin offering a music streaming service to customers.