If AT&T buys DirectTV, it could go head-to-head with Comcast-Time Warner Cable

AT&T may be getting more involved in the pay-TV business with a bid for DirecTV. If that's true, it could have major implications for the US TV market.

Merging with one of the nation's biggest satellite TV providers would put AT&T on strong footing to compete against an expanded Comcast (if the cable company successfully buys Time Warner Cable).

AT&T has about 5.7 million TV customers on its U-verse service, while DirecTV boasts about 20 million subscribers. A combined Comcast-Time Warner Cable would control about 30 million customers. The mergers would create two big giants, each controlling around one-third of the US pay-TV market.

One big question is whether AT&T could get a merger past federal regulators, who are already looking closely at the proposed Comcast deal.

A serious move by AT&T to pursue DirecTV (more on that in a bit) would trigger a pretty complicated game of regulatory chess: The Federal Communications Commission and the Justice Department would probably need to determine whether or how an AT&T-DirecTV merger would affect a Comcast-TWC merger.