Google has launched Android Pay, making the mobile payment system available in more than one million locations in the US.

With a market worth an estimated $1 trillion, Android Pay will be a direct competitor to Apple's own system; Apple Pay.

It allows Android smartphone users with near-field communication (NFC) and the KitKat 4.4+ operating system to store their credit card and loyalty card information securely on their phone to pay for items by tapping the phone to a contactless card reader.

Existing Google Wallet users will be able to access Android Pay through an update, and new users will be able to download Android Pay over the next few days.

Google is yet to announce when Android Pay will be available outside of the US. For now, customers shopping in places like Macy's, Bloomingdale's, Subway, McDonald's and Nike will be able to use the system.