The search giant has unveiled a new payments tool that lets developers of mobile apps and sites allow people paying for items to use a stored credit card in their Google Accounts. The news was announced at Google’s annual developer conference, I/O, in Mountain View, Calif. on Wednesday.

As Sridhar Ramaswamy, Google’s senior vice president of ads and commerce, explained in an exclusive interview with Fortune, the new technology lets those hundreds of million of users who have stored a credit card with their Gmail, YouTube, or Google Play account be able to quickly purchase items within Android apps or on a mobile website.

Users will see a “Pay with Google” button on apps where the new payments tool has been integrated and will be able to choose a credit card to pay with by logging in with their Google account email and password.

It’s similar in some ways to Android Pay, a mobile wallet Google debuted that lets shoppers upload their credit and debit card information to the mobile app to pay for items in stores. The new API will work for Android Pay users as well, but the payments tool cannot be used for iPhone apps or for the desktop web.

But Ramaswamy said that the goal for this new tool is to enable those people who have credit cards stored in their Google accounts but don’t have Android Pay accounts to be able to pay for items in apps easily. “We’re going for more reach,” he said simply.

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It makes sense for Google to encourage all of the accounts with credit cards stored for other purposes—such as renting cloud storage and buying movies or TV shows. The mobile payments industry is expected to reach $3.4 billion by 2022, and Google has the potential to own the wallet that powers these payments because its services are so widely used. Instead of asking consumers to add credit cards to their accounts, Google is just turning the credit cards that are already stored into digital wallets.

The new, broader wallet will continue to compete with other mobile wallets, such as Apple Pay or PayPal.

“In the mobile world, more and more consumers want things to be seamless and secure,” Ramaswamy said. “There’s a big initiative inside Google to have more consumers be logged in to be ready to initiate commerce anytime.”

Along with a new payments, tool, Ramaswamy also revealed that Google’s mobile advertising platform AdMob, a service for embedding ads in mobile apps, has paid over $3.5 billion in ad revenue to developers. Google also said that it would start putting ads for apps on the homepage of its iTunes-rival Google Play, as well as on an app install page. Previously, Google Play only offered ads in search.

Update (May 17, 2007, 3:46 PM): This story’s headline was changed to remove a reference to Gmail.