Microsoft is in talks to buy up to 5 percent of Facebook in a deal that could value the fast-growing online social network company at $10 billion or more, the Wall Street Journal reported on Monday. The move could give maturing Microsoft more access to young users and let Facebook get closer to a major software maker at a time when its growth is increasingly tied to a proliferation of small applications from independent developers on its site.

Citing people familiar with the matter, the Journal said the world's largest software company sought to buy a stake of up to 5 percent in Facebook for $300 million to $500 million.

Facebook may insist on a valuation as high as $15 billion and is considering raising up to $500 million in cash to expand its operations, according to the Journal.

Such a deal could help Microsoft better compete against Web search leader Google for a growing base of online advertising and put one of the Internet's hottest names in Microsoft's camp.

Facebook, which already has an advertising deal with Microsoft, would benefit from closer ties with developers as it seeks to turn its site into a full-fledged Web platform where users can play games, interact and read news about each other.

Google has also expressed an interest in investing in Facebook, the Journal report said.

Facebook has grown to 39 million members, up nearly 63 percent from 24 million in late May, and is quickly gaining ground on larger rival MySpace, which was taken over by News Corp in 2005 for what is now seen as a bargain price of $580 million. MySpace has more than 200 million users.

Microsoft also has an agreement with popular news site Digg.com.