Apple's Tim Cook is expected to kick off his reign as chief executive on Tuesday by unveiling a hot new iPhone model that some analysts are predicting will be a bestseller.

Cook will be filling the shoes of legendary Apple co-founder and pitchman Steve Jobs, who surrendered the California company's helm in August due to health reasons.

Jobs, 56, who underwent an operation for pancreatic cancer in 2004 and a liver transplant in 2009, remains with Apple as chairman of the board of directors.

Apple is holding the event in an intimate auditorium at its Cupertino headquarters and has invited only select press to be present for Cook's on-stage debut as chief executive.

"For a moment tomorrow, all eyes will turn toward San Francisco and most activity will cease when Apple introduces the iPhone 5," said analyst Roger Kay of Endpoint Technologies Associates.

"This event will be Tim Cook's first time out as the undisputed leader of Apple, and so it will be a test for him," Kay added.

The iPhone 5 is what analysts and others have taken to calling the new generation in Apple's sizzling smartphone line.

Apple, as usual, has provided only the scantest of hints regarding what to expect at the event.

Speculation includes talk that Cook will unveil a new iPhone with more processing power, increased touchscreen size, and ramped up camera quality.

Gadget lovers are keen to see whether the iPhone 5 will work on high-speed "4G" telecom networks.

A survey by leading mobile advertising network InMobi indicated that 41 percent of smartphone users in Canada, Mexico, and the United States plan to buy an iPhone 5.

Ticonderoga Securities analyst Brian White sent out word to investors that pent-up demand for a new iPhone model could fuel record shattering sales the day it hits stores.

"However, if Apple only unveils a product update -- akin to the 3GS version of the iPhone that Apple released in 2009 -- interest in the new smartphone will be significantly lower," InMobi cautioned.

A bargain-priced version of the iPhone may also be planned to capture money-minded buyers.

While smartphone fans are eager for slick new iPhones, the major launch at the event could be that of an "iCloud" service that lets people access music, photos, calendars, and other digital files from any Apple devices.

"The big thing isn't the iPhone at all, it is the iCloud," said analyst Rob Enderle from Enderle Group in Silicon Valley. "From everything I am hearing, it is great."

Apple has said previously that iCloud will be available "this fall."

Hope that Steve Jobs will make a surprise appearance has provided a backdrop of drama for the event. Enderle, an admitted outsider when it comes to Apple, doubted Jobs would join 50-year-old Cook at the event.

"This will really be the first time that it is really clear that Steve Jobs is not coming back," the analyst predicted.

Jobs's mastery at getting people to see all that is wonderful about Apple products and overlook potential flaws will be missed if the new iPhone model doesn't synch with carriers behind fast new mobile data networks, he said.