Google may have jumped the gun with its Wednesday announcement that all major credit cards are now accessible via its Google Wallet app. American Express Denies Signing on for Google Wallet Expansion.

Google may have jumped the gun with itsWednesday announcement that all major credit cards are now accessible via its Google Wallet app.

As TechCrunch first reported Thursday, American Express, named as one of the mobile wallet's top four services, disputed its partnership.

American Express spokesman Bradley Minor told PCMag today in a statement that "while we are interested in the technology and remain in discussions with them [Google] about opportunities to work together, we did not provide approval to be included."

The company's biggest issue seems to be how Google's updated online billfold handles multiple credit card types, TechCrunch pointed out. Google Wallet's in-store purchases are actually propped up by a virtual prepaid MasterCard PayPass account, through which all transactions run. American Express seems to be uncomfortable with the fact that not all pertinent purchase information is carried over with the transaction amount, TechCrunch said.