Apple’s CEO Tim Cook has revealed one million credit cards were activated on Apple Pay in its first three days.  So far, the US’ six biggest credit card issuers have signed up, with a reported 500 financial service providers joining early next year. Visa, MasterCard and American Express are among those already enabling the app.

Apple commenced the payment service in the US on October 20, allowing customers make purchases at 220,000 shops or through apps by using the iPhone 6 and 6 Plus, and thumbprint recognition.

Despite its infancy, Apple Pay is already facing fierce market competition. Merchant Customer Exchange, a mobile technology firm owned by some of US’ biggest retailers, will launch a similar service, called CurrentC, next year that can be used on both Android and Apple phones.

With this in mind, Apple Pay is not accepted in pharmacies including Rite Aid and CVS Health, although some customers managed to make payments through the app until the functionality was disabled by the retailers.

Apple, however, didn’t seem too concerned about the competition. “I think it’s a skirmish,” Cook retorted when questioned at the Wall Street Journal’s Gerry Baker at the newspaper’s WSJD Live event. “In the long arc of time you’re only relevant as a merchant if your customers love you,” Cook said, indicating he thinks some of the retailers might still change their minds.

The prospect of having to use a separate system that saves retailers monies on credit card handling charges admittedly isn’t greatly appealing. Anything in this space needs to be consumer-led for it to really take off. Some consumers might also find it off-putting if a payment app is directly linked to a customer loyalty programme, although it is not clear whether this would be opt-in in the CurrentC service.

Meanwhile, Jack Ma, the founder and CEO of Chinese internet wholesaler Alibaba has indicated it wants to join Apple Pay. “We’re going to talk about getting married later this week,” Cook said. “We love to partner with people who are wicked smart, with flexible teams, who are product-based, who push us, and we push them. … Jack has a company that’s exactly like that.”