Apple has denied it has outright rejected the Google Voice app for the iPhone, and told regulators on Friday it is under review because it could interfere with the "user experience".
In its letter to the FCC, Apple said: "Contrary to published reports, Apple has not rejected the Google Voice application, and continues to study it.
"It appears to alter the iPhone's distinctive user experience by replacing the iPhone's core mobile telephone functionality and Apple user interface with its own user interface for telephone calls, text messaging and voicemail."
It also said that Google's appropriation of the iPhone's entire contacts database raised privacy concerns and that it had yet to receive assurances from the search giant regarding how it would be used.
Meanwhile in its letter, AT&T, the iPhone carrier in the US, specifically denied it had any hand in the decision not to offer Google Voice via the iPhone App Store.
"AT&T was not asked about the matter by Apple at any time, nor did we offer any view one way or the other," it said.
Many commentators pointed the finger at AT&T when the block was reported in July, alleging it was seeking to avoid competition. Google Voice offers free calls and texts, potentially damaging the carrier's main revenue sources.
Google Voice wouldn't be the first third part call app for the iPhone, but rivals such as Skype for iPhone only allow calls via Wi-Fi. The Google Voice app would connect to the internet via the AT&T 3G network. Apple said it was unclear whther Google Voice actually uses VoIP.
Apple confirmed AT&T's denial of involvement in its letter. However, it acknowledged it was contractually obliged "not to include functionality in any Apple phone that enables a customer to use AT&T's cellular network service to originate or terminate a VoIP session without obtaining AT&T's permission".
Apple and AT&T sent their letters to regulators in response to a broad investigation of competition in the US wireless market. ®