Just hours after Verizon Wireless announced Tuesday a $99.99 unlimited calling plan for its gabbiest customers, two chief rivals -- AT&T and T-Mobile USA -- matched the offer.

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AT&T, whose wireless division is based Atlanta, said it would begin offering those customers who just can't seem to put their phones down a $99.99-a-month deal by Friday.

Like Verizon Wireless' plans, AT&T's will let its customers call at anytime, seven days a week, with no caps on minutes.

"This is a highly competitive market and we're committed to moving fast to meet customer needs," Ralph de la Vega, president and chief marketing officer of AT&T Mobility, said Tuesday in a statement.

T-Mobile followed suit soon afterward with a similar plan. Sprint Nextel Corp., which has tested unlimited plans in some states, reportedly was considering its options late Tuesday.

Verizon Wireless early Tuesday announced it was offering the new unlimited plan to get consumers who needed more minutes than have been traditionally offered, even with the most generous plans. The company estimated that target audience to be about 15 percent of cellphone users, or more than 30 million people.

Previously, MetroPCS and other smaller carriers offer unlimited calling, but only in specific cities and regions.

The nation's wireless companies are in a fierce battle for subscribers. AT&T is the nation's largest with 70.1 million subscribers. Verizon Wireless is close behind with 65.7 million customers. T-Mobile has 28.7 million subscribers, and Sprint had 54 million subscribers at the end of the third quarter, the latest figure available.

The quick responses by competitors to the Verizon Wireless move demonstrates the high stakes in the telecommunications industry, analysts said. Doing nothing would have allowed Verizon to steal high-volume users, they said.

"Just for defense purposes, the other carriers had to respond really quickly," said Roger Entner, senior vice president for the communications sector for IAG Research.

Entner guesses that Sprint, which had been widely rumored to have a national plan under consideration before Verizon beat them to the market, is probably looking at how to one-up the competition.

"The question for Sprint is how much?" he said.

Jeff Kagan, a metro-Atlanta based analyst, cautioned that consumers should keep this in perspective.

"This is an exciting day in wireless," he said. "But remember, this is only really for the small group of very heavy users. Not everyone. Not yet."