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Apple has run out of white iPhone 4s on the eve of the launch of the hot-selling next-generation smartphone, the latest hiccup in the gadget's closely watched global roll-out.

Apple said on Wednesday that supplies of its more popular black model remain ample.

The company moved 600,000 units of the slimmer and better-equipped $199 iPhone 4 in its first day of pre-sales, a deluge of interest that jammed ordering systems and squeezed carrier partner AT&T's Inc's inventory.

The well-reviewed iPhone 4 goes on sale on Thursday in five of the world's biggest economies -- China and its guarded telecommunications sector being a notable exception -- and consumers hoping to score the device are expected to throng stores.

"White models of Apple's new iPhone 4 have proven more challenging to manufacture than expected, and as a result they will not be available until the second half of July," the company said in a statement.

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The iPhone is Apple's main growth driver and is expected to soon become its biggest source of revenue. The latest version begins selling in the U.S., Japan, France, Germany and Britain this week but will be in 88 countries by September -- the company's fastest-ever global product roll-out.

Shares in Apple were down 1 percent at $270.81 in afternoon trade, after gaining more than 1 percent on Tuesday.