Apple will be looking to tighten its grip on the tablet market on Friday with the release of its newest iPad, increasing pressure on Google to make rival Android devices more enticing.

Hordes of gadget lovers are expected to lay siege to Apple stores to get their hands on third-generation iPads when they debut at 8:00 am local time in the United States and nine other countries including Australia and France.

A week later the new iPads will be available in nearly 30 more countries.

It has become standard to see long queues at Apple shops on release dates, and a flood of orders for iPads at the California firm's online store indicates the ritual will continue on Friday.

"If pre-orders are any indication, we are going to end up with a heck of a lot of people lined up at the stores," said Gartner analyst Van Baker.

"A lot of people are going to be curious in addition to those that want to buy one," Baker said. "There will be big crowds for a while."

A key upgrade to the new iPad is eye-grabbing screen resolution on par with that of an iPhone 4S, and it needs to be seen to be appreciated, according to Baker.

The new iPad also boasts a more powerful processor and the ability to connect to the latest 4G LTE telecom networks that move data faster than their predecessors.

A high-energy launch is vital to Apple, since the tablets are the company's second-best selling device after iPhones in a wildly successful but extremely narrow product line, Baker said.

Apple's online shop quickly sold out of iPads available for delivery on Friday and began telling buyers they will have to wait several weeks.

Analysts at Canaccord Genuity predicted Apple will sell 65.6 million iPads this year, raising their forecast by nearly 10 million tablets after the unveiling of the latest model.

"We believe Apple has extended its leadership position in the fast-growing tablet market," Canaccord Genuity said in a note to investors. "We believe the new iPad has raised the bar relative to competing tablets."

Makers of tablets powered by Google-backed Android software have produced impressive hardware, but lack the "ecosystem" of applications, movies, and music available for iPads.

About 200,000 fun, hip, or functional "apps" have been tailored for iPads while the number of mini-programs customized for Android tablets is estimated at anywhere from 200 to 2,000.

Part of the challenge is that free Android software has been customized by gadget makers to suit the array of tablets, meaning app developers need to do the same with programs.

In contrast, an app can be designed to work on all iPads.

"Google is going to have to do something to foster additional development of applications on Android tablets," Baker said.

"Something is going to have to give on that front to increase the appeal of Android tablets other than the Kindle Fire."

Kindle Fire tablets from Amazon have racked up sales by costing hundreds of dollars less than the cheapest iPad and by being synched with the rich trove of movies, music, digital books and more sold by the online retail colossus.

Industry tracker IDC said that Android tablets are slowly closing the gap with iPads thanks to the Kindle Fire and could take the lead in terms of global market share by the year 2015.

"The sheer number of vendors shipping low-priced, Android-based tablets means that Google's OS (operating system) will overtake Apple's in terms of worldwide market share," IDC mobile connected devices research director Tom Mainelli said.

Apple is offering a 16-gigabyte iPad 2 model for a trimmed price of $399 in a move which "should expand the market for the product as well," according to NPD analyst Ross Rubin.

New-generation iPads are being sold at the same prices as previous models, which start at $499 for a basic model featuring wireless connectivity only.