More than a dozen major retailers Wednesday announced plans to create a mobile payments network that will challenge other m-payments initiatives, including Google Wallet and Isis, backed by mobile carriers Verizon Wireless, AT&T and T-Mobile USA.

The Merchant Customer Exchange, led by retailers including Wal-Mart, Target, 7-Eleven and Sears, aims to develop a smartphone application that would allow mobile purchases across participating stores, as well as enabling offers, promotions and retail programs.

The merchants behind MCX, which The Wall Street Journal first reported on in March, are counting on existing relationships with customers to provide an edge over rival mobile wallet projects.

MCX, which already lags behind similar ventures, has set no launch date and has not yet appointed a CEO, according to a Journal report today. Nor is it clear how much each participating company is contributing to the payment network's development.

The announcement comes on the heels of Starbucks forming an alliance with m-payments startup Square to allow the coffee chain's customers to make purchases through the Pay With Square app. Starbucks is also investing $25 million in Square and will use its technology to eventually process all credit and debit transactions.

To deal with the growing array of competing m-payment projects, the Electronic Transactions Association just formed a Mobile Payments Committee to develop industrywide solutions and standardize policy and business models for the emerging space. The major wireless carriers, credit card companies and banks have signed on, including Verizon, AT&T, Visa, MasterCard and Wells Fargo. The new MPC group doesn't include any retailers.