UK Android Pay users can now add American Express cards to the app for use with mobile payments at supported retailers and websites. That being said, there are AMEX cards which are and are not supported, so users will want to make note of that. Of the supported cards included are UK AMEX cards which are issued as personal cards or those which are issued as small business cards, as well as charge cards and corporate cards. Those that are not supported are pre-paid AMEX cards, virtual cards, corporate purchasing cards, and meeting cards.
If you live in the UK and are wanting to set up an American Express card with the Android Pay app then all you should have to do is open the app and tap the floating action button to add a new card, then either take a picture of the card as the app will suggest or enter the card details manually. If the app still tells you that the American Express cards are unsupported it may be that the app isn't on the latest version and it may have to be updated. It is worth mentioning though that the support for American Express cards in the UK was not highlighted by the Android Pay team or Google in any way so it would be easy to miss if you weren't checking on your own to see if they work.
UK users being able to add AMEX cards to Android Pay follows the ability for users in Canada to add AMEX cards to the app, which happened earlier this Summer, specifically back on June 28th. In addition to recently adding AMEX support in Canada and now in the UK, U.S. Android Pay users recently had the opportunity to start taking advantage of some new promotions that Google was offering for the service, allowing users to make purchases with Android Pay and receive special deals, such as $3 off a movie ticket when purchasing a ticket through Fandango with Android Pay, or $5 off your next three food orders through the DoorDash service. If you're a user in the U.S. and want to add an American Express card to the app, AMEX cards have already been supported for some time and the only cards listed which aren't compatible are prepaid cards.