AT&T Inc. said it would make its unlimited data plan available to all wireless customers who pay a monthly bill, days after rival Verizon Communications Inc announced an unlimited option.

Previously, AT&T's plan, which includes unlimited data, talk and text for $100 a month for a single line, only applied to its DirecTV and U-Verse subscribers. Starting on Friday, it will be expanded to other customers.

On Sunday, Verizon said it would offer an unlimited plan for the first time in more than five years. Analysts said the news reflected an intensifying price war in the wireless industry that could put more pressure on major players to cut costs.

Shares of AT&T, Verizon, Sprint Corp. and T-Mobile US Inc. were flat in after-hours trading.