Best Buy will being selling the Apple iPhone 3G beginning Sept. 7, making it the only retail store in the United States other than Apple and AT&T stores to carry the hot handset.

The deal is exclusive through this year’s December holiday season, according to Best Buy spokesman Jeff Dudash.

Currently the big-box electronics specialist is training its employees and generally ramping up smartphone sales, officials said.  Pricing will be the same as from Apple and AT&T directly – $199 for the 8 GB phone and $299 for the 16 GB version, plus a new 2-year contract.

The iPhone will be sold in all of the chain’s 970 stores, Dudash said, as long as they are in areas with AT&T coverage.  But unlike anyplace else in the United States, it will be displayed among several other phones and carriers, including competitive models such as Verizon’s LG Dare and Sprint’s Samsung Instinct.

It’s unknown if Apple will expand retail sales of the iPhone in 2009. An AT&T spokesman declined to elaborate, according to the Associated Press.  Also not clear at this point is whether Apple will design its marketing differently for Best Buy, given the numerous choices on adjacent shelves.

Apple could not be reached for comment.