London-Facebook plans to integrate its messaging services on Instagram, WhatsApp and Facebook Messenger, BBC reported Friday.

While all three will remain stand-alone apps, at a much deeper level 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 of 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, reported the NYT, and is expected to be completed by the end of 2019 or early next year.

Mr Zuckerberg is reportedly pushing the integration plan to make its 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, suggested Makena Kelly on tech news site The Verge.

"We want to build the best messaging experiences we can; and people want messaging to be fast, simple, reliable and private," said Facebook in a statement.

"We're working on making more of our messaging products end-to-end encrypted 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.

Linking the three systems marks a 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 championing of the plan to connect 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 at a fundamental level may prompt regulators to take another look at its data handling practices.

In June, the NYT reported  Mr Zuckerberg planned to integrate the social network’s messaging services — WhatsApp, Instagram and Facebook Messenger — asserting his control over the company’s sprawling divisions at a time when its business has been battered by scandals.

The move, described by four people involved in the effort, requires thousands of Facebook employees to reconfigure how WhatsApp, Instagram and Facebook Messenger function at their most basic levels.

A Facebook user could send an encrypted message to someone who has only a WhatsApp account, for example. Currently, that isn’t possible because the apps are separate.

By stitching the apps’ infrastructure together, Mr. Zuckerberg wants to increase the utility of the social network, keeping its billions of users highly engaged inside its ecosystem. If people turn more regularly to Facebook-owned properties for texting, they may forgo rival messaging services, such as those from Apple and Google, said the people, who declined to be identified because the moves are confidential. If users interact more frequently with Facebook’s apps, the company may also be able to build up its advertising business or add new services to make money, they said.