Soon after the announcement of Verizon's (VZ) unlimited plan, AT&T (T) has announced it will expand access to its unlimited plan starting February 17. Previously the carrier only offered bottomless plans to subscribers of its DIRECTV or U-verse TV services.

"We're offering unlimited entertainment on the nation's best data network where and when you want to enjoy more of what you love," said David Christopher, chief marketing officer of the AT&T Entertainment Group in a statement. (See also: Verizon Launches Unlimited Data Plan)

The plan offers unlimited calling, texting and data. It also includes unlimited calls from the U.S. to Canada and Mexico, plus unlimited texting to over 120 countries. Just like Verizon's plan, it will allow users to stream HD videos. Its default resolution downgrading software Stream Saver will be active on these plans but can be turned off for no additional cost. Since Verizon's announcement, both Sprint (S) and T-Mobile (TMUS) have added HD streaming to their unlimited packages. (See also: Sprint One-Ups T-Mobile's Unlimited Offer)

At $100 for a single line, it's currently the most expensive unlimited data plan to be announced. Adding a line costs $40 until the fourth line which is free of cost. For comparison, Verizon will be charging $80 a month for a single line, while T-Mobile charges $70, and Sprint charges $50. Like every other carrier, there is a cap on the data at 22 GB after which data is prioritized, the same as Verizon and nearly the same as Sprint (23 GB), though slightly lower than T-Mobile (28 GB).

This week has seen all major carriers enhance their data plan offerings in a bid to outdo each other. While the other carriers allow tethering, or the sharing of data with other devices, AT&T's plan only allows it for connected cars, which tech website The Verge called a "disappointment." Considering the fact that Sprint, T-Mobile and Verizon's plans offer tethering of up to 10 GB LTE and are all cheaper than AT&T's new plan, customers may not be as tempted by AT&T.

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