After only one day with a limit of one iPhone per customer, AT&T, the exclusive iPhone seller outside of Apple in the United States, said Thursday the restriction has ended.

The telephone company said it went back to its old policy of three per customer after it found that it had enough iPhones to resume normal sales. AT&T enacted the stricter limit Wednesday.

"Our No. 1 concern is to make sure that every customer who wants an iPhone gets one," an AT&T spokesman said. "We thought yesterday that the fairest way to do that was to limit customers to one iPhone. Then we realized that we have sufficient inventory to go back to our original policy."

He declined to discuss inventory levels at AT&T or reports of iPhone shortages in the United States and the United Kingdom, which has led to speculation that Apple is reducing inventories to make way for a new version of the smartphone that would ship next month. "We have sufficient inventory, and we continue to have them in our stores," he said.

The telephone company notified its retail department of the limit through an internal memo distributed Wednesday and obtained by the Apple enthusiast site AppleInsider. The spokesman declined comment on the memo.

"Effective May 14, 2008, customers can only purchase one iPhone at AT&T stores," the memo said, according to AppleInsider. "The prior limit of three iPhones is no longer in effect."

In addition, AT&T Wireless stores were told not to accept cash or checks, but only credit and debit cards for iPhone purchases, the memo said. If sales reps wanted to sell more than one device to a customer, they would have to get approval from a director or general manager.

Apple chief executive Steve Jobs is scheduled to give a keynote address at the company's Worldwide Developers Conference June 9 in San Francisco. Some analysts believe Jobs will unveil the company's new iPhone then.

IPhone shortages have been reported in the United States and the United Kingdom, and Apple is no longer accepting orders through its online store in both regions. The shortages and suspension are believed to be the result of Apple reducing inventories of the current 8-GB and 16-GB phones to make room for the new version, which analysts predict will be capable of processing higher data speeds on carriers' 3G networks. The current iPhones access so-called 2.5G networks, which are far slower than 3G. The latter is closer to wired broadband speeds.

Apple's U.K. wireless partner, O2, reportedly ran out of iPhones last week and is now selling only the high-end version, which has the larger storage capacity.