Jennifer Van Grove/CNET

Calling all teens and cheapskates, Facebook has updated its Messenger for iPhone application to allow people in the U.S. to make free voice calls to their social network friends.

Facebook members with Messenger for iPhone will find a "Free Call" button located on friends' contact info pages inside the application. A click of the button will dial up the contact in question over Wi-Fi or your phone's data connection.

Facebook started rolling out voice calls to its U.S. members today, according to The Verge. The voice-over-IP feature was first made available to Canadian users in early January as a test but is now deemed ready for phone tag in the states.

The calling functionality makes Messenger into more than just an SMS or iMessage challenger. Now Facebook is potentially a bona fide threat to carriers. But the bigger play here is for teen attention.

With free calling, Facebook has built itself a large enough straw to drink out of the fountain of youth. Teens carry around iPod Touches and smartphones with limited or shared voice and data plans. Even if texting is their first love, they probably still want to make actual phone calls on occasion.

Though similar free-calling services have been available for some time -- through Gmail chat, for instance -- Facebook's offering seems better positioned to reach youngsters where it matters most: on a handset connected to their friends list.

Ultimately, the update could ensure that teens spend more time using Facebook, which skews older than competitors in the social-networking world.

Messenger for iPhone with free calling is available now to U.S. users and does not require an application update through the App Store.