Prototypes of the third-generation iPad are already in circulation among members of Apple's supply chain, it has been claimed.

Analyst Mark Moskowitz of JP Morgan reckons that the iPad 3 won't be launched until the summer of next year, as Apple is in no hurry to launch the device.

His comments, reported by Apple Insider, suggests that industry insiders - and certainly Apple - think that the competition are so far behind the iPad that rushing out a third-generation model would be premature.

"In our view, Apple should be in no rush. The other tablet entrants have stumbled so far, and that trend-line could persist deep into 2012," Moskowitz said.

Earlier this year, it was thought that Apple could be planning to launch the iPad 3 before Christmas and perhaps as early as this month. However, it was later claimed that shortages of key components would prevent a 2011 launch.

But it is thought that most of the components have been selected and certified, perhaps including a thinner, lighter battery and a higher-resolution display, which will be similar to the iPhone 4's Retina display.

Moskowitz believes that the forthcoming Amazon tablet could be a realistic challenger to the iPad, but he thinks that Sony's recently-launched tablets will fail.

"To us, Sony's tablet lacks the refined, sleek feel of the iPad and its bezel-like back is not user-friendly. The sony tablet runs on the Android OS, which has failed to garner as much interest in tablets as it has in smartphones," he said.