Zuckerberg and Facebook chief operating officer Sheryl Sandberg have been under pressure to address the issue since headlines broke over the weekend about Cambridge Analytica and its harvesting of some 50 million Facebook users' data.
Cambridge Analytica, a political consulting firm financed by billionaire conservative activist Robert Mercer, was used by the Trump campaign in the 2016 race for the White House.
Facebook is facing a growing backlash on Capitol Hill as more lawmakers demand that Zuckerberg testify. Some are calling for increased regulations on big tech companies.
"Mark Zuckerberg needs to testify under oath in public before the Judiciary Committee. He owes it to the American people who ought to be deeply disappointed by the conflicting and disparate explanations that have been offered," Sen. Richard Blumenthal, D-Connecticut, told reporters Monday. The former Connecticut attorney general warned, "Zuckerberg ought to be subpoenaed to testify if he won't do it voluntarily."
Meanwhile, the hashtag #DeleteFacebook has been spreading on social media. Even the founder of WhatsApp -- which Facebook bought in 2014 for $19 billion -- tweeted: "It is time #DeleteFacebook." However, it's not yet clear whether a significant number of Facebook users have actually abandoned the social network.