Alleging that the combination of American Airlines and US Airways would harm consumers and thwart competition, federal and state regulators on Tuesday filed suit to block the $11 billion deal that would create the world’s largest airline.

“We simply cannot approve a merger that would result in U.S. consumers paying higher fares, higher fees and receiving less service,” said Justice Department Antitrust Division chief William Baer, speaking during a conference call with reporters. “By challenging this merger, the Department of Justice is saying that the American people deserve better.”