AT&T has agreed a deal to expand into Mexico with the acquisition of local carrier Iusacell. The $2.5 billion move will create the first ever "North American mobile service," AT&T says, and it will serve more than 400 million people across the U.S. and Mexico.

As part of the deal, AT&T will take on Iusacell's 8.6 million subscribers as well as its wireless properties, which cover around 70% of Mexico's 120 million citizens. Iusacell uses the same GSM-based infrastructure that AT&T does in the U.S., though it doesn't yet offer 4G LTE connectivity.

Iusacell will remain headquartered in Mexico, but it's unclear at this point whether the carrier will retain its name, or be rebranded. Whatever the case may be, customers on either side of the border will be able to take advantage of each other's networks. In addition, employees of both companies will benefit from "global career development opportunities."

"Iusacell gives us a unique opportunity to create the first-ever North American Mobile Service area covering over 400 million consumers and businesses in Mexico and the United States," said AT&T chairman and CEO Randall Stephenson. "It won't matter which country you're in or which country you're calling – it will all be one network, one customer experience."

AT&T hopes to complete the deal in early 2015, it says, following the approval of Mexican telecoms regulator Instituto Federal de Telecomunicaciones (IFT) and the National Foreign Investments Commission.