Supply problems overseas are putting a crimp in the availability of iPhone 4s, creating big headaches for Apple at the same time that iPad availability is finally improving, flying past the three million mark in July.

AppleInsider is reporting that the iPhone 4 continues to be a hard item to come by, as anyone who has ventured out in an effort to get one probably knows. As a result, at least one analyst is lowering their sales estimates on the handset for the current quarter as a result of ongoing supply chain problems overseas.

Kaufman Bros. analyst Shaw Wu told investors Tuesday that he was “shifting iPhone assumptions to later quarters due to the ‘high likelihood’ that screen supply constraints and inventory drawdown will impact shipments over the next two quarters.” Wall Street is banking on 8.5 million iPhone sales for the quarter that just ended in June, but Wu now anticipates a number closer to 7.5 million, down from an earlier prediction of nine million.

Such a downward shift would be bad news for Apple, who shipped a record 8.75 million handsets last quarter and is likely counting on higher numbers based on the insatiable demand for the new iPhone 4.

"The reason why we believe the inventory drawdown this time will be more impactful than previous drawdowns, is because this product transition involves two entirely new products: the iPhone 4 and iPhone 3GS," Wu explains. "The new iPhone 3GS with 8GB of storage is an entirely new model compared to the previous-generation 3GS with 16GB and 32GB of storage. With the new storage capacity, this is not as simple as taking the previous product and marking the price down."

The news is much better on the iPad front, where analyst Wu is raising his own forecast for the June quarter to 3.5 million, up from 3.3 million. Overall, he expects that 10 million iPads will be sold in 2010, a slight bump in his earlier estimates of 9.7 million. Wu claims there is stronger than expected demand for the Apple tablet, but that availability is improving at last.

Apple announced in late June that they had sold three million iPads in the first 80 days it was on sale -- a remarkable feat considering that only three weeks earlier, the company announced it had sold two million units in the first two months.

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