Apple Inc. is jumping into the mobile-payments market just as retailers upgrade their cash registers to be more secure and ready to receive wireless transactions.

Chief Executive Officer Tim Cook is planning to unveil new iPhones, wearable devices and a mobile-payments system on Sept. 9, people with knowledge of the matter have said. Visa Inc., MasterCard Inc. and American Express Co., as well as banks and retailers, are forming partnerships with Apple to let shoppers pay with iPhones, and possibly using a device worn on the wrist, a person familiar with the plans said this week.

Apple is targeting a market that's projected to jump to $90 billion in 2017 from $12.8 billion in 2012, according to Forrester Research Inc. The dynamics are changing now, as most credit card issuers push U.S. merchants to upgrade their payment terminals to accept chip-based debit and credit cards. Those are more secure and usually capable of handling near-field communication, or contactless, transactions. New iPhones will also include the wireless feature, the person said.