Apple stores across the US are reportedly running out of stock of iPhones, generating a fresh wave of speculation that the release of a new model of the must-have gadget could be looming.

Piper Jaffray analyst Gene Munster notes that at least 20 of Apple's 180 US retail stores are fresh out of iPhones, leading him to anticipate a new model.

Apple spokesman Steve Dowling moved to dismiss the notion, telling Bloomberg, "We are working to replenish iPhone supplies as quickly as we can. Our stores continue to receive shipments almost every day."

Naturally, these determinations of stock unavailability may actually reflect the logistical impact of the recent Easter break, but with 3G iPhone's this month's hottest rumour, it's inevitable news of short supply should set the Mac world agog.

Munster reports his expectation of new iPhone models, and speculates that by January 2009 Apple will have three models available at different prices in order to broaden the appeal of the device.

The analyst also noted that it took Apple two or three years before it was able to ship iPods in similar quantities to the ship rates it has already achieved with the iPhone.