TechCrunch reports that soon after Google unveiled a new feature on Google Wallet that lets users link any brand of payment card to their accounts, at least one card brand took issue with the new feature.

American Express' social media VP told TechCrunch that his company never actually signed off on any deal with Google that would let Wallet users link their American Express cards to a Google Wallet account.

The crux of the issue appears to be the way in which purchases through Google Wallet are recorded on cardholders' statements. American Express provides very detailed transaction information on customer statements. But for any purchase made using the Google Wallet tied to an Amex card, an Amex cardholder statement will only read "Google" with the merchant name and the transaction amount.

What likely rankles Amex even more about that arrangement is that MasterCard — the brand behind the virtual cards through which Google Wallet purchases are actually made — now gets all that rich purchase data. Amex, for its part, gets handed the transaction (and likely the fees for handling the transaction), but loses all the data that goes with it to a competing card brand.

This is no small thing. Amex (and the other card brands for that matter) offer transaction data to merchants for marketing and partnership programs. Additionally, the ability to tie purchases to online behavior using purchase data is one of the many benefits touted by mobile payments. 

Minor told TechCrunch that Amex Cardholders are free to link their cards to Google Wallet for now, but no official deal is in place between the two companies.

Google sent the following response to TechCrunch:

"For many years, we've accepted American Express, Visa, MasterCard and Discover for online and mobile transactions. The latest version of Google Wallet extends these same benefits to people who choose to use the Google Wallet app to make purchases in-store. We are in active discussions with American Express and look forward to working together as partners as the world embraces digital payments."

For more stories on this topic, visit the carrier/card brands research center.