Swedish music streaming service Spotify is to launch in the United States on Thursday. Spotify reportedly plans a formal announcement for early Thursday morning in the United States, where the service will be made available by invitation and subscription. Founded in 2006, Spotify is one of the world\'s biggest streaming websites and is currently available only in Sweden, Norway, Finland, Britain, France, Spain and the Netherlands because of copyright issues. It said in March it had reached one million paying users. Around seven million people use its free version. Earlier this year, Spotify slapped restrictions on its free version, slashing the amount of times a track can be played and the total amount of music users can listen to without paying. In May, it unveiled an application enabling users to synchronize playlists and songs purchased through its service with Apple\'s iPod, in what industry observers saw as a clear challenge to Apple\'s iTunes. The young Swedish company had previously focused solely on online streaming. Also in May, a report in Forbes based on unnamed sources said Facebook was testing a service that would allow songs from Spotify\'s vast library of music to be streamed to members of the social network.