Facebook is bringing its voice-over-IP calling feature to even more of its users on the Android platform.

On Thursday, the company added the free calling functionality for U.S. users of Facebook Messenger for Android -- and Facebook Home, which runs Messenger, by association. The rollout will take place throughout the day and does not require an application update, a company spokesperson told CNET.

The addition introduces a "Free Call" button accessible from a Facebook buddy's contact page. Those with Facebook Home also can initiate calls from Chat Heads, although it requires several clicks to do so: Click the three dots next to your contact's name, select "Open in Messenger," and then navigate to the person's contact info.

Once you finally get to the Free Call button, Facebook will dial up your friend over Wi-Fi or your phone's data connection.

The social network has been pushing out the free calling functionality to people in various locales since early January. The VoIP option first started as a test for Canadian users of the company's Messenger iPhone app in early January, but has since been added to Facebook's full-featured iPhone app and carried over to Messenger for Android for people in 23 countries. Today's update means the functionality is available to people in 24 countries.

The option offers people a way to make phone calls without using minutes from their smartphone's voice plan, which makes the social network a potential threat to carriers.