Google has said its Voice application for iPhone was rejected by Apple, contrary to a statement Apple made to regulators last month.
According to Reuters, the Federal Communications Commission sent letters to both companies and AT&T, the iPhone's US network provider, requesting an explanation once it heard of the issue.
In documents made public by the FCC last week, Google said Apple representatives rejected the application after a series of meetings, phone calls and emails.
Apple said in a response letter in August that it had not rejected the application and was still studying it following concerns that it replaces the iPhone's core functionality and user interface with its own system for making calls, voicemail, and sending texts.
An Apple spokesman told Reuters that the company still disagreed with Google’s position, and that the app had not been rejected.
The letters from the companies were reportedly a response to an FCC inquiry launched in July, which is looking into competition in the wireless industry.