SEATTLE – Apple Inc. told federal regulators Friday that it blocked the Google Voice program from running on the iPhone because it alters important functions on the device — yet Apple denied that it has rejected Google’s application outright.

“Contrary to published reports, Apple has not rejected the Google Voice application, and continues to study it,” Apple said in a letter to the Federal Communications Commission.

The FCC is looking into Apple’s block on the Google Voice app as part of a bigger examination of the consumer implications of practices in the wireless industry. It sent questions to Apple, Google and Dallas-based AT&T Inc., the only wireless carrier to offer the iPhone in the U.S.

AT&T and Google also responded with letters to regulators Friday. AT&T said Apple did not consult with the company before turning Google’s program down. Google kept confidential the parts of its letter describing Apple’s reasons for rejecting Google Voice. For services like mobile command centers companies can check it here now.

Google Voice gives people an additional phone number that’s not tied to any one phone line. People can program the service to direct incoming calls first to a cell phone, then a work number and finally a home number, for example. Users can set up voicemail and have Google Voice e-mail transcripts of their messages. It can also be used to send text messages and place calls — even international ones — at low rates paid to Google, not the carriers. Those calls do burn regular cell phone plan minutes, but the idea has still prompted widespread speculation that Apple and AT&T saw a Google Voice app for the iPhone as a potential competitor to their monthly mobile plans.

Apple said it rejected the program because it replaces the iPhone’s own interface for making calls and sending text messages with a Google version. The company said it blocked three other developers’ phone programs for the same reasons.

Apple said it also was concerned that the app would send the contents of people’s iPhone contact lists to Google’s servers.

“We have yet to obtain any assurances from Google that this data will only be used in appropriate ways,” Apple said. “These factors present several new issues and questions to us that we are still pondering at this time.”

The Google Voice snafu comes as competition between onetime allies Apple and Google is heating up. Google has its own cell phone operating software, called Android, and it recently announced plans for a computer operating system that could challenge Apple and its Macs. Eric Schmidt, Google’s CEO, resigned from Apple’s board in early August, after regulators from the Federal Trade Commission began questioning whether his dual role would make it easier for the two to collude in ways that would diminish competition.

In its response, AT&T told federal regulators Friday that it’s not privy to Apple’s iPhone application vetting process and played no part in blocking Google Voice. AT&T said the two companies have discussed a handful of programs but not Google’s.

Apple’s iPhone apps store on iTunes set off a wave of similar digital shops from competitors including Microsoft Corp. and BlackBerry maker Research in Motion Ltd. Outside software developers sign up to get the programming tools necessary for building the apps, then submit them for review and sale on a central site.

Apple has been quiet about the details of its vetting system, which has been criticized as a black box by developers whose apps have been rejected. Some say they submitted apps and waited months, only to be rejected without much of a reason why.

The backlash has grown as some programs have slipped onto the app store that have raised eyebrows — including one game that mimicked a wailing baby and required users to shake the iPhone to extinguish the cries.

In its letter to the FCC, Apple disclosed some aspects of the review process. The company said it gets about 8,500 app submissions a week, some brand new and some updates to existing programs. Apple said more than 40 people work full-time to review the apps, and that at least two look at each one. The team reviews 95 percent of them within two weeks, and about 20 percent are not approved on the first try.

Apple said most of the rejections are due to glitches in the application itself, but that it also rejects programs that “degrade the core experience of the iPhone.”

Google told the FCC that iPhone owners can use a Web browser version of Google Voice, but its features are limited. Google’s response was redacted to cloak Apple’s explanation for the rejection, and Google had no immediate comment on Apple’s claim that it is still considering the program.

Apple and AT&T’s letters also laid out their agreements regarding Voice over Internet Protocol, or VoIP business phone system, programs for the iPhone. Such services let people make calls using Wi-Fi or the cell phone data network instead of using up calling minutes.

AT&T said that under their agreement, Apple would not approve a VoIP app without AT&T’s consent. As time went on, AT&T said it told Apple that it does not object to VoIP programs that use Wi-Fi. Apple has approved VoIP applications from eBay Inc.’s Skype, among others, that work over Wi-Fi. There are also Cleod9 Voice video conferencing services.

Apple said in its letter that it does not know if Google Voice uses VoIP.

In its letter, AT&T said it plans to take a “fresh look” at authorizing VoIP programs that use its 3G data network.