In prepared testimony to the House Judiciary Committee’s antitrust panel, Zuckerberg says Facebook has used its infrastructure to improve Instagram and WhatsApp in ways that benefitted users.

“These benefits came about as a result of our acquisition of those companies, and would not have happened had we not made those acquisitions,” says Zuckerberg’s testimony, which NBC News earlier reported. “… The end result is better services that provide more value to people and advertisers, which is a core goal of Facebook’s acquisition strategy.”

For instance, he says, Facebook helped Instagram to control “runaway spam” and build the direct-messaging and video services that are key parts of the app today. Additionally, WhatsApp became free after its merger with Facebook and built voice and video-calling products on Facebook’s technology, according to Zuckerberg.

The billionaire social-media tycoon will deliver the testimony at a hotly anticipated congressional hearing examining the power of tech giants. Zuckerberg will appear along with Google CEO Sundar Pichai, Apple chief Tim Cook and Amazon boss Jeff Bezos.

Some Washington lawmakers have questioned whether Facebook should control three of the world’s biggest social media platforms over concerns about competition and privacy.

Sen. Elizabeth Warren (D-Mass.) cited Facebook as an example of a company that has used mergers to limit competition in her presidential campaign proposal to break up big tech companies. And Sen. Josh Hawley (R-Mo.) pressed Zuckerberg in a meeting last year to sell Instagram and WhatsApp to prove Facebook’s commitment to data privacy, the Associated Press reported.

Zuckerberg reportedly told Facebook staffers last year that he would “go to the mat” in a fight against Warren’s breakup proposal.

Facebook shares rose 0.8 percent in premarket trading to $231.97 as of 7:13 a.m. Wednesday after dropping 1.4 percent Tuesday.