Facebook Inc. Chief Executive Officer Mark Zuckerberg, testifying before a joint hearing of two Senate committees in Washington, hinted at the possibility that there may someday be a version of the social-media app that would be supported by user fees, rather than advertising revenue.

Pressed on whether Facebook will always be free for users and supported by ads, Zuckerberg appeared to leave the way open for a paid version.

“There will always be a version of Facebook that is free,” he said.

Facebook Inc.’s Mark Zuckerberg was prepared to cite competition with China if asked whether the social-media giant should be broken up, according to a photograph of internal notes the chief executive officer took to a congressional hearing on Tuesday.

“Break Up FB? U.S. tech companies key asset for America; break up strengthens Chinese companies,” the document read, according to a picture published by the Associated Press.

Zuckerberg was speaking during the first of two days of testimony to Congress, after a data leak sparked the worst crisis in the company’s history. During a break, he left his notes and some journalists snapped pictures, including an AP photographer.

The memo also advised the CEO to highlight that Facebook is a small part of a much bigger advertising market, and to point out that consumers and marketers have choices.

It provided a figure for Zuckerberg to cite, if necessary: that the overall ad market is worth $650 billion, with Facebook accounting for 6 percent.