Facebook plans to integrate its messaging services on Instagram, WhatsApp and Facebook Messenger.
While all three will remain stand-alone apps, they will be linked so messages can travel between the different services.
Facebook told the BBC it was at the start of a "long process".
The plan was first reported in the New York Times and is believed to be a personal project or Facebook founder Mark Zuckerberg.
Once complete, the merger would mean that a Facebook user could communicate directly with someone who only has a WhatsApp account. This is currently impossible as the applications have no common core.
The work to merge the three elements has already begun, the NYT reported, and is expected to be completed by the end of 2019 or early next year.
Cross-platform messaging may also lead the way for businesses on one platform to message potential customers.
And it might make it easier for Facebook to share data across the three platforms, to help its targeted advertising efforts.
But bigger still: it makes Facebook's suite of apps a much tighter, interwoven collection of services. That could make the key parts of Facebook's empire more difficult to break up and spin off, if governments and regulators decide that is necessary.
Shared data
Mr. Zuckerberg is reportedly pushing the integration plan to make his trinity of services more useful and increase the amount of time people spend on them.
By effectively joining all its users into one massive group Facebook could compete more effectively with Google's messaging services and Apple's iMessage, Makena suggested Kelly on tech news site The Verge.
"We want to build the best messaging experiences we can; and people want to be fast, simple, reliable and private," said Facebook in a statement.
"We're working on making more of our messaging products encrypted end-to-end and considering ways to make it easier to reach friends and family across networks," it added.
The statement said there was a lot of "discussion and debate" about how the system would eventually work.
- Facebook ignored kids' spending problems
- Facebook fined £ 500,000 for data scandal
- Will Facebook be fined after hack attack?
Linking the three systems marks and significant change at Facebook as before now it has let Instagram and WhatsApp operate as largely independent companies.
The NYT claimed that Mr Zuckerberg's champion of the plan to connect to the messaging system had caused "internal strife". It was part of the reason that the founders of both Instagram and WhatsApp left last year.
The decision comes as Facebook faces repeated investigations and criticisms over the way it has handled and safeguarded user data.
Comprehensively linking user data to a fundamental level may prompt the regulators to look at their data action practices.
The UK's Information Commissioner has already conducted investigations into how much data is shared between WhatsApp and Facebook