T-Mobile USA is the first mobile operator to sell the card reader for fast-growing payments provider Square. The US operator will start selling the reader, which is targeted at the small-business market, through selected stores from February 7.  When attached to a smartphone the Square reader enables users to process credit card transactions.  T-Mobile will sell the reader with 4G smartphones and tariff plans targeted at small business users. The operator’s 4G service is based on HSPA+ technology. News of the link-up between T-Mobile and Square first came out last month.  The reader will be sold in 113 T-Mobile stores across 15 US states.

The Square relationship adds to T-Mobile’s existing strategies for the mobile payment market. It is also one of the three mobile operators which set up Isis, a NFC-based payments venture. It is also working with payments startup LevelUp on its service.  T-Mobile’s rivals have taken similar approaches. Both Verizon Wireless and AT&T sell a Square-like card reader from a vendor called Intuit. They are also partners with T-Mobile in Isis. Fourth-largest US operator Sprint is working with Google on its wallet service.

In its battle with the likes of Intuit, Square has added T-Mobile’s stores to its existing retail relationships which include Apple, Wal-Mart, Target, Radioshack and Best Buy.