T-Mobile USA will be the first carrier to build a Facebook application into the BlackBerries it sells, but BlackBerry users on any network will be able to download the application starting later Wednesday, Facebook Co-Founder and Vice President of Engineering Dustin Moskovitz said in a keynote address at the CTIA Wireless I.T. and Entertainment show in San Francisco.

In the keynote, Moskovitz demonstrated taking a photo with a BlackBerry Curve device, adding tags to it and posting it to Facebook without even starting up the Facebook application. Other features include the ability to set special ringtones for Facebook events and invite friends to join Facebook through BlackBerry e-mail. But it's the open nature of Facebook's platform, which allows third parties to add new applications, that sets the company apart, Moskovitz said.

The tie-up brings together the highest profile social-networking player, with almost 50 million active users, and an enterprise mobile pioneer vying for market share against Microsoft, Palm, Symbian, Apple and other device and OS vendors. Executives of the two companies met at the CTIA Wireless Show in March in Orlando and agreed to work together, Moskovitz said. Openness is the key factor they had in common, he said.

Starting from a base of thousands of colleges and high schools, Facebook last year opened its network to anyone, and members over 35 years old are the fastest-growing segment, Moskovitz said. RIM has its roots in corporate e-mail tied to specialized enterprise servers, so the partnership could help Facebook grow right where it's catching up.

The announcement came amid reports on Wednesday that Google and Microsoft are wooing Facebook.

Facebook also announced a few other advances in the mobile arena, where it expects to have 4 million active users by the end of this month. There are Facebook services available on most major U.S. and Canadian carriers, and Moskovitz announced its first carrier deal outside North America, with O2 (U.K.).

One extension announced Wednesday lets users add information from third-party Facebook applications as a box in their mobile profiles. As an example, Moskovitz showed a user's profile that listed two causes he supports. Another extension lets organizations text-message Facebook members to send a text message in support of a cause. The member's support is immediately reflected on Facebook on the Web, he said.