The Merchant Customer Exchange (MCX) – a consortium of leading US retailers that last month announced plans to launch their own mobile payment service – has announced new members, including clothing giant GAP.

A Reuters report notes that the group now has 21 publicly traded members. New additions include Bed Bath & Beyond, Dunkin' Brands Group, Dillards and convenience store operator Sheetz. Initial members included Wal-Mart, Target, Best Buy and 7-Eleven.

There is still no word on a launch date, but the alliance hopes to battle similar US mobile payment services from Google Wallet and Isis (the venture between the country’s leading mobile operators).

"One of the reasons why there has not been widespread adoption of mobile payments is because the experience is not yet seamless for consumers," a spokesman for MCX told Reuters. "We think (MCX) will help in adoption of mobile payments."

The initiative promises to develop a mobile wallet that in addition to payments will provide a range of offers, promotions and retail programmes. A mobile wallet app will be available for "virtually any smartphone", says the new company.