Apple today announced an expansion of its mobile payments service Apple Pay in two new countries, Australia and Canada, for owners of American Express cards. CEO Tim Cook broke the news on Apple's fourth-quarter earnings call today, saying the company wanted to bring Apple Pay to more "key global markets."

Apple Pay, which lets users make payments either online or in-store using iPhones and iPads with a fingerprint sensor, has been available in the US since its launch in October 2014. The service was extended to UK users in July of this year, and Apple is now increasing the speed of the rollout. Following Australia and Canada, American Express plans to bring Apple Pay to card owners in Spain, Hong Kong, and Singapore starting in 2016. It's unclear when Apple will expand Apple Pay to more banks and credit cards for these countries considering it supports almost every major financial institution in the US and UK.

The adoption rate of Apple Pay is an open question as the company has kept usage numbers under wraps, though the company has said the service is seeing "double-digit growth in transactions month after month." There has been speculation that the service isn't spreading fast. According to market researcher Phoenix Marketing International, only 14 percent of US households with credit cards have signed up for Apple Pay, up three percentage points from February.