Leading US mobile operator AT&T has started selling the Square card reader at more than 1,000 of its retail stores, a further step in the latter's efforts to become the leading payments acceptance tool for small businesses. The card reader is already available at more than 20,000 retail outlets including branches of Apple, Wal-Mart, Target and Best Buy.

AT&T is not the first operator to sell the Square device. It follows rival T-Mobile USA which started offering the Square reader through selected stores in February this year. The card reader enables small businesses to process card payments via smartphone or tablet. The card reader is attached to the mobile device via the headphone jack.

Separately, AT&T is set to open a flagship store in Chicago that will be radically different from any of its more than 2,300 existing retail outlets in the US. The idea is to put less emphasis on handsets and push user interest towards the services offered by the operator. For example the shop has an Apps Bar, as well as a series of "boutiques" covering areas such as health & fitness, the connected car, the operator's U-Verse broadband and TV service and its Digital Life home platform.