Best Buy is expected to announce an agreement with Apple to start selling iPhone 3Gs in 986 stores starting on September 7th.

Best Buy has just completed a major upgrade of their “Best Buy Mobile” departments, which may have been a part of this deal. Best Buy already sells some other high-end phones, such as the Samsung Instinct, so it makes sense that Apple would want to put their own device out there as well.

The official announcement is expected as early as tomorrow.