NTT DoCoMo and Microsoft are working together to make mobile phones compatible with online music stores that use Microsoft's technology, they said Thursday.

DoCoMo, Japan's leading mobile phone operator, will begin introducing support for the Windows Media Digital Rights Management 10 system to its phones.

The deal between the two companies extends to DoCoMo's overseas partners in its I-mode alliance, which will consider the use of Windows Media DRM, DoCoMo said. There are around five million I-mode users in 14 countries: Australia, Belgium, England, France, Germany, Greece, Ireland, Israel, Italy, the Netherlands, Spain, Taiwan, Russia and Singapore.

The deal comes as KDDI, DoCoMo's main competitor, is pushing its Lismo service, which lets users download songs to a mobile and transfer them to a PC. Songs can also be transferred to other phones from the PC. The songs are protected using a digital-rights-management system and payment is made via the mobile phone bill.

In Japan, downloading music using a phone is vastly more popular than through PC-based internet services. In 2005, about 96 per cent of the 268 million tracks purchased electronically were downloaded via mobile services, according to the Recording Industry Association of Japan.

Related to Thursday's deal, DoCoMo said it will also consider adding Windows Media Video to future mobile phone handsets.