Facebook is continuing its assault on SMS and quest to become the only messaging app you use today by expanding its “contact via phone number” feature to Messenger for iOS. The option launched on Android to a select set of testers at the end of October, and is being pushed to all Androiders as well as all iOS users. The update is rolling out now and also brings a cleaner layout, and faster start-up and navigation.

The intent is clear. As I detailed last month, Facebook doesn’t want you to have to switch to SMS to contact someone who you have the phone number of but aren’t friends with. It’s watched as startup messaging apps like WeChat and KakaoTalk that rely on phone numbers rise to huge user counts. The move could box them out, if it’s not too late.

WeChat is thought to have over 200M users, while its Chinese parent company Tencent’s desktop messaging service QQ is said to over 800 million active users. WhatsApp is thought to have somewhere between 250 million and 350 million users, while KakaoTalk is said to have over 90 million. Then there’s sticker-messaging app Line, and Snapchat, which sees about as many daily photo uploads and  which the Wall Street Journal today said refused a $3 billion acquisition offer from Facebook.

One reason the Asian messaging startups may be gaining ground is they’re getting users addicted to games. Several have their own internal gaming platforms that third-parties build titles for. Meanwhile, Facebook is pursuing a “social layer” strategy in mobile gaming, hoping to provide login and sharing options to native games rather than running the platform itself. That might not be forceful enough to keep users’ eyes glued while they wait for replies from friends.

Overall, this degree of fragmentation in the messaging market is dangerous for Facebook because it thrives on having all your friends in one place. Messaging generates a ton of user engagment and return visits, plus also helps companies build an accurate social graph of who you talk to most. That’s important data Facebook needs to refine its News Feed relevancy algorithm and ad targeting.

The option to contact someone via phone number within Messenger might dissuade people from using these other apps. It could be especially helpful to budget-minded folks who don’t want to rack up SMS costs. International travelers could benefit from avoiding SMS roaming charges.

At this point, it doesn’t look like Facebook will be able to beat all these messaging competitors. At best it can hope to stunt their growth and hold onto its existing users.