Facebook parent Meta Platforms bought up nascent rivals Instagram and WhatsApp after its attempts to compete had failed, an attorney for the U.S. Federal Trade Commission said at the beginning of a high-stakes trial in Washington on Monday,

The Federal Trade Commission says Meta has monopolized the social-media market—and should be broken up.

Meta Platforms Inc. faces a historic antitrust trial beginning Monday that could force the tech giant to break off Instagram and WhatsApp, startups it bought more than a decade ago that have since grown into social media powerhouses.