SAN FRANCISCO – Apple is expected to unveil its latest take on the iPhone Tuesday during an annual ritual that will probably cast a spotlight on the gadget maker’s drive to regain market share and its sluggish pace of innovation.

In keeping with its tight-lipped ways, Apple Inc. hasn’t disclosed what’s on the agenda for the coming-out party at its headquarters in Cupertino, Calif.

But this is the time of year that Apple typically shows off the latest generation of its iPhone, a device that has reshaped the way people use computers since its debut in 2007. Apple took the wraps off the iPhone 5, the current model, last September. The company has never waited longer than a year to update the iPhone, which has generated $88 billion in revenue in the past year.

Apple’s timetable for rolling out products has vexed many investors who have watched the company’s growth slow and profit margins decrease.

Meanwhile, a bevy of smartphone makers, most of whom rely on Google Inc.’s free Android software, release wave after wave of devices that cost less than the iPhone. Those concerns are reflected in Apple’s stock price, which has declined nearly 30 percent since peaking at $705.07 at about the same time the iPhone 5 went on sale last year.

Even though Apple’s market value of roughly $460 billion is more than any other company in the world, the deterioration in its stock price is escalating the pressure on CEO Tim Cook to prove he’s the right leader to carry on the legacy of co-founder Steve Jobs.

Since Cook became CEO two years ago, Apple has only pushed out new versions of products developed under Jobs.

The company is believed to be working on a so-called smartwatch that would work like a wrist-bound smartphone. Samsung Electronics, one of Apple’s biggest rivals, introduced its $300 smartwatch called Gear last week.

The company isn’t expected to reveal the latest model of its tablet computer, the iPad, until later in the fall. Apple introduced a smaller, less expensive version of the iPad last year in response to the success of more compact and cheaper tablets run on the Android system.

This year’s refresh of the iPhone line may address the growing popularity of cheaper Android phones. Based on leaks from suppliers, it appears Apple is poised to release a less elaborate and less expensive version of the iPhone in an attempt to appeal to consumers too frugal or too poor to pay for the high-end model that sells for more than $600 without a wireless contract.

If reports published in technology blogs and newspapers pan out, the stripped-down iPhone will be called the “5C” and will be housed in plastic casing, in a variety of colors, instead of an aluminum casing.

If it introduces a cheaper iPhone, Apple might end production of the iPhone 4 and iPhone 4S that were released in 2010 and 2011, respectively.

A new version of the high-end iPhone also is expected to be revealed Tuesday. The top-of-the-line model, expected to be dubbed the “5S,” will be the first to be sold with Apple’s revamped mobile software, iOS 7, already installed.

The new system, which will automatically update apps installed on the device, can be downloaded on the iPhone 4 and later models, as well as on tablets, beginning with the iPad 2.

There is also speculation that the high-end iPhone will be sold in a golden color to supplement the product line’s more prosaic choice of black or white. If there is a gold iPhone, it would be the latest sign of Apple’s intensifying focus on China. The color gold is considered to be a sign of good fortune in China.