Isis mobile payments adds American Express

American Express has just made good on its promise to support the mobile payment platform Isis.

The biggest competitor to Google Wallet has just joined forces with American Express to have the three biggest credit card issuers already flipping the switch with its mobile payment platform.

Isis, a joint venture between T-Mobile, AT&T, and Verizon, is steadily making its way to a nationwide launch.

The platform was officially lit up during the SXSW conference in Austin, Texas earlier this year. But it was mainly a demonstration just for that event.

It is currently looking for a more robust launch in Austin, as well as fellow test city Salt Lake City, later this year. And today’s announcement means that when that happens, you’ll be able to add your American Express card to your Isis-enabled device.

What that means is when you’re at the store, you can tap your phone at the register to pay without taking out your AmEx.

Select Visa and MasterCard products have also already become Isis-enabled, and Discover announced that it is supporting Isis but hasn’t fully implemented the technology yet.

Because it is a consortium of three of the four major mobile carriers, handset support for Isis is not going to be a problem. The only other major carrier is currently the only one that supports Google Wallet, a platform that will likely fade away as Isis matures.