Integration is according to The New York Times one of the founders' own heart projects by Mark Zuckerberg, and should be part of a longer process designed to extend the time spent by users in different applications.
Interconnection means changing a song for Facebook, which previously allowed the three companies to function largely independently of each other.
It is one year ahead
The project has already begun but is not expected to be completed by the end of 2019 or early 2020 at the earliest.
"We want to build the best chat opportunities and people want the chat feature to be fast, reliable and personal," said a Facebook spokesman.
The company is also trying to calm troubled users with the fact that they are using more advanced encryption for all their chat tips.