Apple Inc. has lined up an impressive list of banks and credit-card issuers to support its new mobile-payment service. Now all it needs is more merchants, and customers.

Apple hopes its service, Apple Pay, will prompt shoppers to ditch their wallet and make purchases with an iPhone. The system relies on a technology known as near-field communication, or NFC, that has had trouble winning acceptance from merchants.

Merchants must install a reader at their checkout line for so-called tap-and-go payments. NFC readers are being used by fewer than 10% of merchants, according to Gartner analyst Mark Hung.

Starting in October, Apple said iPhone owners will be able to use Apple Pay at 220,000 U.S. locations, including McDonald's Corp., Bloomingdale's and Macy's. By comparison, the Electronic Transactions Association said more than nine million U.S. merchants accept credit and debit cards.

"Apple has rallied the issuing bank side, but not the merchant side," said Richard Crone, chief executive of Crone Consulting, a payments advisory firm. "Many merchants who had NFC acceptance have turned it off."