Internet social networking leader MySpace is joining Google Inc.'s platform for sharing applications across the Web — a concept that threatens to undermine the rapid growth of their common rival, Facebook Inc.

Google trumpeted the MySpace coup Thursday in a meeting with reporters, just two days after revealing its plans to create a distribution network for other applications. The interactive programs, also known as "widgets," make it easier to share music, pictures, video and other personal interests on social networking sites.

MySpace, owned by News Corp., was conspicuously absent from the initial list of websites that agreed to host the widgets from Google's "OpenSocial" platform.

That raised questions whether MySpace might try to build a proprietary platform for widgets, much like Facebook has already done.

But MySpace and Google executives said they began discussing a system that culminated in OpenSocial more than a year ago. The formal announcement about the alliance was timed to coincide with a party that Google is throwing for software developers Thursday evening in Mountain View.

Google also disclosed for the first time that another popular social networking site, Bebo.com, will host widgets supplied from its platform.

Other previously disclosed social networks participating include Friendster, hi5, LinkedIn, Ning and the Google-owned Orkut.

All told, the potential audience of OpenSocial's network is expected to exceed 200 million.

"The broader story here is that the web has moved to its next stage," Eric Schmidt, Google's chief executive, said.

Google's open-ended approach contrasts with Palo Alto-based Facebook's, which relies on unique coding that has prevented widgets from working on other sites.

Facebook's formula has been highly effective so far. More than 8,000 widgets have been created for its website in the past five months, a drawing card that has fuelled Facebook's growth to about 50 million users worldwide.

Facebook's booming membership encouraged Microsoft Corp. to pay $240 million US for a 1.6 per cent stake for Facebook last week — a deal that valued the three-year-old startup at $15 billion.

MySpace CEO Chris DeWolfe is confident that OpenSocial will transform his site into a hotbed of communal applications.

"OpenSocial will become the de facto standard for developing applications right out of the gate," DeWolfe said.

Facebook was invited to join OpenSocial, said Vic Gundotra, a vice-president of engineering for Google, and Schmidt said the door remains open.

"Everyone is invited to join," Schmidt said. "There has been no effort to discriminate or exclude."

Facebook didn't immediately respond to a request for comment Thursday.