Google Inc., developer of the Android mobile-phone platform, plans to start a subscription music-streaming service as soon as this week that would compete with Spotify Ltd., people with knowledge of the matter said.

Universal Music Group Inc., Sony Music Entertainment and Warner Music Group Corp. have reached agreements to license songs, said the people, who asked not to be identified because the agreement is private. Google will announce the service as soon as Wednesday to coincide with a conference for developers in San Francisco, the people said.

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By offering music, Google is seeking to give consumers more reasons to use the Android operating system, already the most widely used software in smartphones. The company is also challenging online-music providers like Spotify, which lists more than 6 million paying subscribers and more than 24 million active users in 28 countries.

Google's plans to unveil the service this week were previously reported by The Wall Street Journal.

Apple Inc., maker of the iPhone, is also planning a music service that would challenge Spotify in streaming and Pandora Media Inc. in Web-based radio, people with knowledge of the situation said in September.

Google, based in Mountain View, California, climbed 1.1 percent to $887.10 at yesterday's close in New York, leaving the stock up 25 percent this year.