Licensing issues have forced music streaming firm Pandora to shut down its service to users outside the US, the UK and Canada. 

Pandora streams songs to users based on the Music Genome Project software, which analyses the qualities of different songs and groups them for the listener.

The user enters the name of a particular artist or song, and the site streams music with similar attributes and influences.

Pandora will be screening the IP addresses of users in order to keep the service out of markets where it is not licensed to operate.

Tim Westergren, founder of the company, told vnunet.com that Pandora will continue to expand as the company obtains licensing for additional countries. 

However, the expansion is being hampered by a lack of coherent licensing systems in many countries.

"One of the things we hope is that this will highlight the need for some sort of global or regional [licensing] system," said Westergren.

Pandora's efforts to expand are also held back by a 15 July rate hike for web-based music broadcasting in the US.

"In general those benchmarks are something of a standard, so this has put a really big wrinkle into all of that," said Westergren.