Facebook-owned WhatsApp is being censored in China as the Communist Party congress gets underway.

Facebook's WhatsApp now has more than 2 billion users, the app's CEO, Will Cathcart, told The Wall Street Journal in an interview published Wednesday, revealing its user numbers for the first time in two years. The company detailed the milestone in a blog post.

That's just half a billion monthly users shy of Facebook's monthly active users. Cathcart said WhatsApp would continue to operate largely independent of Facebook and continue to defend providing its encrypted messaging service. That aligns with the statements Facebook made in 2014 as it was trying to buy the company for $19 billion.

A spokesperson said "WhatsApp will operate as a separate company and will honor its commitments to privacy and security," according to a letter from the Federal Trade Commission during its review of the merger.

But last year, Facebook's plans to integrate WhatsApp with its other messaging services, Instagram and Facebook Messenger, set off alarms for some antitrust experts. The FTC has made clear it's interested in digging through past acquisitions of tech giants and learning how they emboldened those firms, most recently through a new research study that will look at unreported small acquisitions by Facebook and four of its peers. The FTC is separately probing Facebook for potentially anti-competitive conduct in which investigators are looking into Facebook's acquisitions of WhatsApp and Instagram, according to an earlier Journal report.

Facebook is planning to make the newly integrated service end-to-end encrypted, which has also raised concerns for law enforcement including U.S. Attorney General William Barr, who fear further shielding criminals. Barr asked Facebook to postpone its encryption plans and figure a way to provide "lawful access" to law enforcement to detect crimes like child exploitation.

In the interview with the Journal, Cathcart said he was committed to helping law enforcement by providing metadata but that the risks of building a so-called backdoor could be great, though he declined to comment on what he would do if ordered to create one.

"The alleged perpetrators behind the Equifax attack were, you know, members of the military of China," he said of the hack affecting the personal information of 145 million people. "That targeted, as you know, every American — not specific ones."

Even as Facebook moves to make its products interoperable with WhatsApp, Cathcart told the Journal that WhatsApp has still maintained a level of distance. The company has opted not to implement some of the same features as Facebook's other apps, backing off from a plan to sell ads in the app, for example.

"WhatsApp is best for private communication," Cathcart told the Journal. "We've been willing to make product choices that skew towards the more private."

Read the full story in The Wall Street Journal.

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