The platform is a mobile payments service that works with iPhone and Apple Watch devices in the United States, the United Kingdom, Switzerland, Canada, Australia, China, France, Hong Kong, and Singapore. Apple is also planning to expand the service to Japan.

Apple Pay lets users pay using their phones at retail stores equipped with point-of-sale registers supporting near-field communication (NFC) technology. People simply place their smartphones or Internet-connected watches near the point-of-sale sensors to make a payment without having to swipe a card. Consumers can also use Apple Pay accounts to pay for items within apps and on mobile websites.

Apple Pay has been integrated within thousands of apps, including Best Buy (BBY), Etsy (ETSY), Sephora, Staples (SPLS), Starbucks (SBUX), Instacart, OpenTable, and Target (TGT).

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Reuters recently reported that Apple Pay is struggling to drive usage outside the U.S., facing competition from regional services such as China’s Alipay (BABA) and local banks. The news service estimated that Apple Pay usage volume was $10.9 billion last year, but the majority of those payments were made in the United States.

But Apple has said that it is adding one million new users each week to the payments service, boasting that the transaction volume via Apple Pay is five times the amount from a year ago. However, without a baseline usage number, it’s impossible know whether the current volume is significant.

Apple also faces competition internationally from Google’s (GOOGL) rival service, Android Pay, as well as Samsung Pay (SSNLF). Android Pay is available in the U.S., the U.K., and Australia. Samsung Pay is available in nine countries, including Russia.