Apple's current $999 white MacBook has met with a severe supply constraint at a number of retailers, suggesting a draw-down in stocks ahead of a potential update.

Many of the Apple authorized resellers are completely sold out of the polycarbonate 13-inch MacBook, according to Apple Insider. Specifically, Amazon, MacConnection, On Sale and J&R are all out of stock. In addition, inventory of the entry-level portable is low at DataVision, the website noted.

The shortages have not yet extended Apple's own distribution channels, as its online stores still indicate the availability to ship the notebook. However, shortages at third-party retailers are often the first clue of Apple readying its supply line to release updated models. 

The upcoming launch of Mac OS X Lion, Apple's next-generation operating system, is expected to precede any new hardware update and freeze all new Mac introductions.

Apple has been well overdue for a MacBook refresh - the white MacBook was last updated in May 2010, and its price has been reduced to $899. 

Rumors about a July launch for the new MacBook have been reported, and sources in Apple's upstream supply chain said that component suppliers for the Mac maker will run in full gear next month, according to a report from the DigiTimes. This is because Apple's next generation of Mac Books will be due out in July.

While Apple's Chinese manufacturing partners are ready to ship MacBook Air hardware, Apple is waiting to release the notebooks only after Lion is ready. 

 

Rumors from last week also indicates the debut of next-generation Sandy Bridge powered MacBook Air notebooks will offer a choice of black finish.