According to The Verge, the updated app will allow users to make free voice calls to their friends on Facebook.
To make a call, users just need to open a conversation with the person they want to call, press the "i" button in the right corner and select "free call."
The service allows calls to be made using Wi-Fi or a phone's data connection.
"We started testing this in Canada the first week of the year and today we're extending that test to the US," Facebook told The telegraph in an email. "We were able to expand the test so quickly because it went well in Canada and we wanted to expand the audience."
The new service is currently only available to iPhone users in the US and does not offer video calling like Skype.
The Facebook Messenger App is available for free at Apple's app store.
The launch of its voice calling service comes after the network released its graph search feature for the site.
The Graph search allows users to do specific searches about friends on the site by using key phrases. For example, a person can search for "people from my hometown who like skiing" or even "friends of friends who like surfing."
The search gives users access to over one billion people, 240 billion photos and more than a trillion connections when searching on Facebook.
"Facebook's mission is to make the world more open and connected," said the company. "The main way we do this is by giving people the tools to map out their relationships with the people and things they care about. We call this map the graph. It's big and constantly expanding with new people, content and connections."
The search tool differs from web search because users must use phrases instead of keywords. Once a user has entered a specific phrase they are then given a set of people, places, photos and other content that has been shared on Facebook.
"When Facebook first launched, the main way most people used the site was to browse around, learn about people and make new connections. Graph Search takes us back to our roots and allows people to use the graph to make new connections."
Facebook asserts that most of the content made available when using the new search tool will not be made public. The company says that users will only be able to see what they could already view elsewhere on the social network.
The move by Facebook puts the company in direct competition with Google and Bing while massively increasing their advertising appeal.
"Facebook Graph Search is not a web search engine, but a search tool designed to enrich the Facebook platform and experience for both users and advertisers," said Eden Zoller, principal analyst at Ovum. "This is sensible as a full blown web search engine from Facebook would inevitably have to compete with Google search, and given Google's dominance of the search market it would be hard for Facebook to make a serious impact - and win advertising dollars."
"Before the arrival of Facebook's Graph Search, the search function on Facebook was basic and as such, a wasted opportunity given Facebook's imperative to strengthen advertising revenues," she added. "Facebook Graph Search will no doubt leverage member data to provide advertisers with more targeted, personalized advertising opportunities going forward."
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