Apple Pay saw “a significant acceleration” in usage during the second half of 2015, with a growth rate that was 10 times higher than the first half, said CEO Tim Cook during the company’s fiscal first-quarter earnings call.

Apple’s payment service debuted in the US in October 2014 before launching in the UK last summer. Most recently, it launched in Canada and Australia, but only for American Express cardholders.

Some consumer research has suggested that its take-up in the US has plateaued following early demand from die-hard fans of the company’s products. The Apple chief’s comments appear designed to address that issue.  He did not explain the reasons for the increase in growth.

“Consumers have spent billions of dollars with Apple Pay,” said Tim Cook. He did not reveal how much revenue the company has made from the payment service, as opposed to the volume of transactions it has handled.

Key to spreading the service is reaching agreement with card-issuers, mainly banks. In addition, Apple needs to ensure that point-of-sale terminals are upgraded for NFC technology.

Apple users can now make contactless payments at over 5 million locations in the countries where the service is live today, and will soon be accepted at thousands of Exxon and Mobil branded stations across the US via the Speedpass+ app, added Cook.