News Corp's MySpace, the world's largest social network Web site, said it has formed an online music venture with three major recording companies in a challenge to Apple's dominant iTunes Music Store.

Vivendi's Universal Music Group, Sony BMG Music Entertainment and Warner Music Group have minority stakes in the new MySpace Music venture announced on Thursday. Financial terms were not disclosed.

MySpace Music will offer free music and video streaming supported by advertising, paid-for MP3 downloads, ringtones for cell phones, concert ticket sales and merchandise.

Chris De Wolfe, chief executive of MySpace, said the launch date of the new service was "fluid" with commercial features being added to the site over the next three to four months. He said MySpace is in talks with more music industry partners to offer their services on MySpace Music.

"We're talking to all the big ticketing companies as well as the small ones," De Wolfe said in an interview. He declined comment on EMI, the fourth big music company, which is not in the initial deal.

MySpace will integrate its 5 million artist profile pages with a range of new commercial services in a "360-degree" offering for the 30 million music fans who use the site.

While the online teen hangout has been wildly popular with both music fans and artists, its main role has been promotional until now.

"It goes from being a promotional vehicle to being a commercial vehicle," MySpace COO Amit Kapur said on a conference call to announce the venture.