On Tuesday, assorted Apple retail store locations reported that they had iPhone 3G units in stock to sell. In contrast, wireless carrier AT&T reported that it is filling back-orders from two weeks ago and lacks supplies in its brick and mortar locations.

According to Macworld UK, as of 12:30 A.M. eastern standard time on Tuesday, all 190 U.S. Apple stores showed iPhone 3G phones in stock. Apple's own inventory-checking tool reported that 56.8% of the stores had all three models on hand.

As recently as two weeks ago, Apple's inventory widget claimed that only 23% of Apple's U.S. retail locations had any iPhone 3G units in stock.

AT&T, on the other hand, hasn't been able to replenish its in-store stock for walk-in purchases since the iPhone 3G's July 11th launch last month. Instead, the company is using its supplies to fill back orders placed by customers, according to a spokesman for the company.

Buyers can order an iPhone 3G at an AT&T store using the company's direct fulfillment program wherein the store notifies the customer when the iPhone 3G has arrived. Once the unit is in stock, the customer must return to the store to pick up and activate the phone. "We continue to deliver iPhones to direct fulfillment customers every day," said AT&T spokesman Wes Warnock in an email Tuesday. He acknowledged that stores don't have iPhones for sale to impulse buyers.

The company's backlog currently stands at 13 to 15 days according to a current message updated daily on the company's web site.

If you've gone through this experience yourself, let us know about it over in the comments or forums.