San Francisco, Mar 7 (IANS): Even as Mark Zuckerberg laid out plans to let people reach their friends across Messenger, Instagram or WhatsApp from whichever app they prefer, the Facebook CEO hinted that the interoperability of apps could be possible only on Android devices.

While Messenger is Facebook's messaging platform, both Instagram or WhatsApp are Facebook-owned platforms with massive user base.

"We plan to start by making it possible for you to send messages to your contacts using any of our services, and then to extend that interoperability to SMS too. Of course, this would be opt-in and you will be able to keep your accounts separate if you'd like," Zuckerberg wrote in a blog post on Thursday.

Today if you want to message people on Facebook you have to use Messenger, on Instagram you have to use Direct, and on WhatsApp you have to use WhatsApp.

There are privacy and security advantages to interoperability, Zuckerberg said.

"For example, many people use Messenger on Android to send and receive SMS texts. Those texts can't be end-to-end encrypted because the SMS protocol is not encrypted. With the ability to message across our services, however, you'd be able to send an encrypted message to someone's phone number in WhatsApp from Messenger," he added.

However, there are several issues Facebook will need to work through before this will be possible.

"First, Apple doesn't allow apps to interoperate with SMS on their devices, so we'd only be able to do this on Android," he said.

Zuckerberg said that Facebook will have to address other issues including safety and spam vulnerabilities before making the apps interoperable.