Microsoft on Tuesday launched a video-sharing service that would challenge the popular YouTube in the fast-growing market for online amateur and professional video.

In launching Soapbox, Microsoft has its eye on the success of YouTube, which from January to June grew 297 percent to a monthly unique audience of 19.6 million, according to Nielsen/NetRatings. Key to YouTube's success has been the ability for registered users to upload video and share it with friends.

"Microsoft is jumping on the bandwagon without knowing where it's going, but confident that it needs to be onboard," Joe Wilcox, analyst for JupiterResearch said.

The mystery for sites like YouTube, and now Soapbox, is in making money. While attaching advertising to video sharing is an obvious choice, such a move could offend users, which tend to be teenagers and young adults, and drive them to competitors. Other issues include copyright violations.

Videos uploaded to YouTube often include clips from TV shows, music videos and other copyrighted material. While the site takes down such material upon the request of copyright holders, there have been some rumblings in the entertainment industry over YouTube's failure to prevent such postings to begin with.

Nevertheless, such impressive growth rates are sure to attract challengers like Microsoft, which introduced Soapbox by invitation only in the United States. People interested can sign up for the service, which the software maker expects to expand to an initial group of 5,000 testers in the next week, "throttling up to 10s of thousands and 100s of thousands very quickly," Rob Bennett, general manager of Entertainment and Video Services for MSN, said.

Microsoft plans to implement a copyright protection policy similar to YouTube's, taking down unlicensed content at the request of copyright holders, Bennett said. Both services will also offer the same basic uploading and sharing functions.

Soapbox, however, would have the advantage of integration with Microsoft's portfolio of online services, including its blogging and instant messaging services called Spaces and Messenger, respectively.

In addition, Soapbox has its own player for uploading, searching and sharing video, which a person can do while watching a video. "It's a little more dynamic, fun and engaging (than YouTube)," Bennett said.

Users can rate videos and tag them, so they can be easily found later. Links to videos can be sent via email, and the Soapbox player can be embedded in a Web site or blog. Soapbox can be accessed through Internet Explorer 6 or Firefox 1.0.5 or later. Users will have to be running either Windows XP or Macintosh OS X.

Bennett believes Microsoft can make money immediately after Soapbox's launch by taking content off the site, and displaying it on MSN Video, which generates more ad revenue than any other feature on the Microsoft portal. The Soapbox platform could also be used, for example, to conduct ad-supported contests involving video creation.

Soapbox has its own player for uploading, searching and sharing video, which a person can do while watching a video. Users can rate and comment on videos, and tag them, so they can be easily found later. Links to videos can be sent via email, and the Soapbox player can be embedded in a Web site or blog.

Microsoft plans to integrate Soapbox throughout its portfolio of online services, including its blogging and instant-messaging services called Spaces and Messenger, respectively. Soapbox will be available through MSN Video.

"By adding a user-uploaded video service, we are rounding out our existing investments in commercially produced and original content on MSN Video," Rob Bennett, general manager of Entertainment and Video Services for MSN, said in a statement.

Soapbox can be accessed through Internet Explorer 6 or Firefox 1.0.5 or later. Users will have to be running either the Windows XP or Macintosh OS X operating system.

The number of online video services has grown dramatically, driven in part by TV networks, movie studios and other content providers adopting the Internet as a distribution channel. All the major Internet portals, such as Yahoo, Google, AOL and MSN, offer professional videos.

YouTube owes its growth to providing an easy way for people to upload and share their own home videos. User-generated content sites that offer platforms for photo and video sharing and blogging, comprised five of the top 10 fastest growing Web brands in July, according to Nielsen/NetRatings.

YouTube, however, is also starting to offer video from major entertainment companies. The site on Monday said it had struck a deal with Warner Music Group Corp. to distribute the latter company's music video library, which includes works from such artists as Paul Simon, Madonna and Red Hot Chili Peppers.