Walmart is the largest retailer in the world with 11,723 stores strung around the globe. Daniel Eckert who is senior vice-president of Walmart Services claims that the store enrolls tens of thousands of new users each day. Walmart Pay is already available in 4,774 U.S. stores.Eckert said about surpassing Apple Pay: “If daily enrollments don’t slow down, I think that’s pretty well in the cards shortly. I would have to imagine we are getting pretty close.”Walmart is the largest retail chain that does not accept Apple Pay. Walmart entered the mobile payments market a whole year after Apple. Apple has discussed the integration of Apple Pay into Walmart Pay back in March last year, but ended talks apparently due to problems combining the different technologies used by the two companies.Apple may be concerned that Apple Pay is not available in a retailer that has an estimated 14.5 percent of the U.S. food and grocery market according to estimates by Global Data Retail.In June of this year, 5.1 percent of Walmart shoppers used the Walmart Pay app. This compares with 5.5 percent of iPhone users who used Apple Pay at stores accepting Apple Pay, according to a recent survey.Walmart Pay has an advantage in that it can be used not only on phones with iOS operating system but also on the many Android based phones as well. Apple Pay can only be used on iPhones.Growth of the mobile payments systemThe mobile payment system market has faced some difficulty becoming established among consumers. This is in part due to security concerns as well as the relative ease with which credit or debit cards can be used. Compared to competitors such as Apple Pay and Samsung, Walmart has constant contact with customers and can demonstrate the payment method and directly answer consumer questions.Apple is growing its customer base as well. Apple claims that Safeway will soon use Apple Pay. Starbucks already uses Apple Pay, as does Best Buy and Maceys.Apple Pay active users have more than doubled in the last year, and annual transactions have grown fourfold, Apple claims.Roughly 66 percent of consumers who adopt Walmart Pay end up using the service again within 21 days.There are other competitors in the field including Pay with Google and Square that has developed the Square Register meant to replace the traditional cash register.The market for mobile payments is estimated at about $49 billion.