Apple is expected to launch a new service, currently being dubbed iRadio, at WWDC on 10 June, according to a bevy of reports in the New York Times, Wall Street Journal and Apple fan blogs.

The service will supposedly let people stream music for free but force them to listen to adverts every so often.

Sources familiar with the matter have told the New York Times and WSJ that Warner Music Group - one of the biggest labels on the block with acts such as Muse and Madonna on its books - has now signed up to the service. Others are expected to follow in the days running up to the annual developer conference held by Apple in San Francisco.

Apple has also reportedly signed a deal with the Universal Music Group for its recorded music rights, but not for music publishing - the part of the business that deals with songwriting.

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Apple's plans for an internet radio service have supposedly been in the works for the past year, but have hit hurdle after hurdle.

Negotiations with the music labels have been slow and focused on a number of issues, including royalty rates and a cut of advertising.

Apple is a fairly latecomer to the streaming music business even though it dominates online music sales. It joins services like Spotify, Google, Pandora, Deezer, Napster and others in offering music to people who don't want to buy individual tracks.

Perhaps interestingly, the rumours speculate that Apple's service will be free and ad supported rather than opting for the subscription-based monthly fee as so many already do, which might give it an interesting weapon in the upcoming battle for market share.