AT&T's reign as Apple's exclusive iPhone partner in the United States could be coming to an end soon if rumors from insider sources are to be believed. Apparently Apple is set to announce it is opening the iPhone to other U.S. cell service providers during its special media event in San Francisco on January 27, according to HotHardware.

While the unnamed sources seem certain that the exclusive deal AT&T has had with Apple since the iPhone was first introduced, they didn't offer any information on who Apple may be bringing into the iPhone fold. There has been speculation that Verizon would be the second U.S. iPhone partner, but the company's proprietary cell network isn't compatible with current iPhone models.

Apple could be planning on building a special iPhone model just for Verizon's network, or it could be planning on updating the iPhone with hardware that supports AT&T and Verizon's networks. Thanks to Apple's tight-lipped policy on future plans, however, no one knows for sure what the company has in store for the iPhone.

The special media event Apple will be hosting this Wednesday was announced with invitations hinting at a new product, and the general consensus is that the company will use the event to finally unveil its long-rumored tablet device. There has been speculation that iPhone OS 4.0 will be introduced as well.

Be sure to check in with The Mac Observer on Wednesday for our product announcement coverage.