AT&T expanded its unlimited data plan offer across its mobile customer base, responding to market leader Verizon’s own unlimited tariff which launched earlier this week.

Previously AT&T, the US’ second largest player, offered an unlimited data, talk and text plan costing $100 a month, but it was limited to DirecTV and U-Verse customers as part of a bundled TV package.

In a statement, the operator said the plan was now available to all consumer and business postpaid customers, and will cost the same as Verizon’s package when taking out a contract of four lines, at $180. Breaking the offer down, it will cost customers $140 for two lines, and $180 for three lines, with the fourth line free, the company told Engadget.

However, AT&T tallies up as the priciest offering on the market for a single line, with a price of $100.

Verizon’s offering costs $80 a month, while T-Mobile US’ and Sprint’s tariffs are even cheaper.

AT&T added it “may slow speeds during period of network congestion” after 22GB of data usage a month, the same as Verizon.

T-Mobile, which pioneered the return of the unlimited plan last year with the launch of its One package, said it would de-prioritise customers on their network after 28GB of use.

Like Verizon, AT&T offered unlimited data in the past, but then moved to tiered data packages in 2010. With consumers accessing more video, games and other content on their smartphones, unlimited is making a comeback in the US in particular.

“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, CMO at AT&T.