The Infinite SMS app, which cost US$0.99 and let users send unlimited text messages from an iPod or iPhone, quickly became one of the 10 most-downloaded apps in the iPhone Store after its release last month, developer Inner Fence said in a on its Web site.

But the company stopped sales of the app on Monday after Google notified it that the program would be blocked, Inner Fence said.

"Google has claimed no grievance with Infinite SMS other than its success. Their given reason for the block isn’t abuse or wrongdoing; it’s that we brought too many users (and thus too much cost) to an experimental service," Inner Fence said.

The company said it built the application using an open protocol made available by Google for just such a purpose. "We never could have guessed that the two of us would write an app too big for Google," the company's founders said.

Google said it would continue to offer free SMS through Google Talk, but it will block Infinite SMS and other non-Google clients that use the service to deliver text messages starting on Wednesday.