AT&T Inc. agreed to buy the consumer fiber operations of Lumen Technologies Inc. for $5.75 billion, expanding its fast broadband service in major cities like Denver and Las Vegas. AT&T will pay cash for the unit of Lumen,

The US broadband market is rapidly consolidating, leaving fewer choices as six of the top 10 internet providers were involved in recent acquisitions.

AT&T will buy substantially all of Lumen’s mass markets fiber business for $5.75 billion in a move it says will accelerate high-speed fiber internet access for millions of Americans.