Apple Inc. said its mobile-payment service is now available in more than 2 million retail locations, with merchants such as Crate & Barrel, Chick-fil-A and Au Bon Pain rolling it out in stores.

Online retailer Zappos.com added Apple Pay on its iPhone and iPad apps Tuesday as competition intensifies among mobile payment providers. Globally, mobile payments will increase to $620 billion in 2016 from $450 billion last year, according to a report from TrendForce.

“We’ve been getting requests from customers to use Apple Pay for quite a while,” said Aki Iida, head of mobile for Zappos. “It makes the customer experience easier, why not try it?”

Apple is highlighting services like payments amid slowing sales of the iPhone, which generates more than two-thirds of the Cupertino, California-based company’s revenue. Apple last month forecast its first sales decline in more than a decade, spurring investors to question what the company will do next to revive growth.

In addition to pushing past its goal to make Apple Pay available in 1.5 million retail locations by the end of 2015, the company said the feature’s in-app purchase volume more than doubled in the last six months of the year compared with the first half.

Changing Habits

Still, most U.S. consumers are reluctant to use their smartphones to make routine payments at retail stores. And most in-store terminals don’t yet accept Apple Pay.

“The challenge for us and Apple as well is to see how much the feature is adopted — not just by retailers but also consumers,” Iida said. “Consumers have to change their mindset, that this is a feature they want to use.”

In October, 16.6% of people who own newer iPhones had tried Apple Pay, an increase from 9% in November 2014, according to a survey by Pymnts and InfoScout, a consumer researcher. The service has been expanding globally.

Iida said he may consider working with Apple’s rivals, such as Google’s Android Pay. Competition is intensifying, with JPMorgan Chase & Co. scheduled to introduce its mobile wallet later this year and Wal-Mart Stores Inc. rolling out its payment service nationwide.

Eventually, every large bank and retailer could have its own mobile wallet, said Richard Crone, CEO of researcher Crone Consulting LLC. Those services may compete with or incorporate Apple Pay, and Apple’s strategy is to get into as many of these wallets as possible to grab a piece of the action.

Subscribe Today to Mobile Strategies 360 and Receive Exclusive Data. Not only will you get the latest information on the rapidly changing mobile industry, you will also receive Mobile Market Insights a free monthly overview on the market. These fact sheets are filled with data and statistics to help you identify opportunities and get a jump on the competition. Mobile Market Insights is available only to Mobile Strategies 360 subscribers. Once you enter your free subscription, click on the link for your free download.

Be sure to follow us on Twitter and LinkedIn and be the first to know when new Mobile Strategies 360 content is published.