The MacRumor website said shipping times were being pushed back within an hour or so after the iPhone 5 became available through pre-orders.
CNN reported Saturday that the iPhone's shipping debut would be Friday, Sept. 21, and that Bust Buy and Walmart were among the retailers taking in-store pre-orders.
Apple, Verizon, Sprint and AT&T all began taking pre-orders online Thursday.
Apple and AT&T have warned that pre-orders will not be shipped for two to three weeks, while Verizon has pushed back its shipping expectations to Sept. 28.
Sprint was holding out on Sept. 21, but only for two models. Its website said the 16G version would take "up to two weeks," for shipping.
How much this will diminish the long lines at stores on Sept. 21 has yet to be seen.
The demand for new iPhones has given way to a small side business of entrepreneurs who advertise on Craigslist they will, for a fee, stand in line for someone at a store selling iPhones.