Facebook is reportedly working to make messages across Facebook Messenger, Instagram and WhatsApp work together, a strategy that the social network says could improve privacy but also keep users within its ecosystem of applications.

Facebook CEO Mark Zuckerberg is overseeing the move to create an underlying platform to integrate the company's messaging systems, The New York Times reported Friday, citing four people involved in the project.

Thousands of employees are at work on the strategy, which is in its early stages, the Times reported, but is expected to be completed by the end of 2019 or in early 2020.

All three apps will have end-to-end encryption to prevent outsiders from reading messages. Upon completion, Facebook users could send an encrypted message to someone on Instagram or WhatsApp and vice versa, sources told the Times.

Those apps all have separate messaging systems currently. Integrating them could keep users within Facebook's ecosystem – it paid $19 billion for WhatsApp in 2014 and $1 billion for Instagram in 2012. That integration would not only increase user activity within Facebook's applications, but also give the company potential revenue generating opportunities through increased ad sales and new services, sources told the Times.

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Such synergy could connect billions of users and, perhaps, impact competitors such as Apple and Google. Facebook has about 1.5 billion daily active users, while WhatsApp, the world’s most popular messaging app, has 1.5 billion users. About 500 million use Instagram daily; 800 million use it at least once a month.

“We want to build the best messaging experiences we can; and people want messaging to be fast, simple, reliable and private," Facebook said in a statement to USA TODAY. "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. As you would expect, there is a lot of discussion and debate as we begin the long process of figuring out all the details of how this will work.”

But users input different information to use the apps – personal information such as name, age, relationship status, work history are used on Facebook and to a lesser extent, Instagram, while a cell phone number is used for WhatsApp.

Facebook's ability to compile a more robust user profile across the three messaging services could raise concerns. The company continues to face criticism over the Cambridge Analytica scandal, involving a U.K. political firm and exposure of personal data of an estimated 87 million Americans to manipulation for political purposes during the 2016 election.

Facebook in November 2018 also said it had removed 85 accounts on Instagram and 30 on Facebook that the company feared were linked to Russian operatives and were covertly orchestrating online activity on the eve of the U.S. midterm elections.

WhatsApp has had issues, too. The assailant in March 2017's London terror attacks that killed four and wounded dozens more reportedly used WhatsApp. And last week, WhatsApp said it would limit the number of recipients in forwarded messages to five, down from 20. That came after India experienced violence last summer after viral hoax messages resulted in more than a dozen lynchings, CNN reported.

WhatsApp said it decided to move forward after a six-month test of the five-recipient limit in India. Facebook had been testing the five-forwarding limit in the country after it experienced violence last summer after viral hoax messages resulted in more than a dozen lynchings, CNN reported.

When Facebook acquired WhatsApp and Instagram, Zuckerberg said those companies would remain independent.

In recent months, the co-founders of those apps have departed as concerns over the Cambridge Analytica scandal shook consumer confidence in Facebook.

WhatsApp co-founder Brian Acton, who left the company last year to start a foundation, urged people to delete their Facebook accounts in March 2018 over privacy concerns and gave an push to the #DeleteFacebook movement. WhatsApp CEO and co-founder Jan Koum left a month later.

Instagram's co-founders Kevin Systrom and Mike Krieger resigned in September 2018 and the sources told the Times that internal concerns about Facebook's growing designs led to their departures. WhatsApp employees have also raised concerns about the plan on internal message boards and during a staff meeting last month, the Times reported.

The move could put too much messaging power in the hands of one company, suggests Peter Singer, co-author of "LikeWar: The Weaponization of Social Media." While an integration would help Facebook align its policies, it could suggest "monopoly concerns," he said in a post on Twitter on Friday.

Most users wouldn't "think twice about" the integration of Facebook's trio of apps, says Forrester senior analyst Jessica Liu. But the encryption of messaging is a double-edged sword. The development "is both good and bad: Good for privacy-minded users," she said in an analyst note sent to USA TODAY. "Bad for perpetuating bad (and untraceable) actors/activity on these messenger apps."

Facebook's plan to integrate messaging across the three services could lead to additional scrutiny from lawmakers, which last year called Zuckerberg and other executives from Twitter and Google to testify before Congress.

“We have heard a lot from Facebook about how it is committed to changing course and protecting its users’ information, but the company repeatedly has ignored its promises," said Sen. Edward Markey , D-Mass., in a statement Friday. "Now that Facebook plans to integrate its messaging services, we need more than mere assurances from the company that this move will not come at the expense of users’ data privacy and security. We cannot allow platform integration to become privacy disintegration.”

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Follow USA TODAY reporter Mike Snider on Twitter: @MikeSnider.