Verizon Wireless fired the first shot of what may become an unlimited calling plan price war in the United States today. Verizon is offering a national unlimited calling plan with no roaming or long-distance fees for $99.99 a month. While other carriers have what they call “unlimited” plans, Verizon is the first major carrier to make the deal nationwide.

The plan is “likely to have repercussions for years to come,” Sanford C. Bernstein analyst Craig Moffett wrote in a research report, adding that in the short term, it will force Sprint Nextel Corp. to match the offer.

Sprint has an unlimited plan that costs $119.99 a month that includes unlimited Web use, e-mail and messaging, but is only available to residents of Philadelphia, Minneapolis, Tampa and parts of Northern California. Verizon’s plan doesn’t offer the extras. The small carrier Helio LLC, a company that rents time on Sprint’s network, is offering a $99 a month unlimited plan nationwide which includes unlimited Web use, e-mail and messaging.

Moffett thinks Verizon’s new unlimited plan will make pricing service much easier to understand for the average consumer. Moffett said it is similar to Sprint’s introduction of flat-rate long-distance prices for landline phones made in the 1990s. He said Sprint’s price structure in the 1990s made it easier to compare prices and hastened a rapid decline in prices.