As Google announced its major upgrade for Google Wallet yesterday -- in which shoppers could use any type of major credit card to load up their smartphone -- American Express confirmed today that it didn't agree to such a deal.

"We want to make sure Google's mobile wallet product meets the standards we set for our card members in terms of the transparency and clarity about transaction detail," American Express' VP of social media communications Brad Minor told CNET in an e-mail. "And right now, American Express does not have an agreement with Google for our cards to be used in the Google mobile wallet."

The crux of the issue may be how Google deals with several credit cards at once. The way the app upgrade works is by aiming to support all credit and debit cards from Visa, MasterCard, American Express, and Discover in the cloud. However, the in-store Wallet transactions are still handled by Google's original partner MasterCard via a PayPass account. So what that means is there's a possibility that not all purchase information is passed along to the credit card actually paying for the transaction.