Credit card company American Express (NYSE:AXP) isn’t too happy with Google (NASDAQ:GOOG) right now. Here’s why:

On Wednesday, Google announced a new cloud-based version of its Google Wallet that it said supports all credit and debit cards from Visa (NYSE:V), MasterCard (NYSE:MA), Discover (NYSE:DFS) and American Express.

The problem with that statement is that American Express had not officially agreed to participate in the new Google Wallet. The card company did partake in past versions of Google’s mobile payments apps like Google Checkout.

American Express spokesman Brad Minor told AllThingsD that “they haven’t gotten our approval for the additional use.” He also said the card company could shut off the feature if necessary.

It’s not clear why American Express wouldn’t want to participate in Google Wallet because the app is pretty much revered as a win-win for both the tech giant and card companies. And if American Express does decide to shut off the feature, that would be a big blow to Google.

Google said in a statement that it’s in “active discussions with American Express and looks forward to working together as partners as the world embraces digital payments.”