Mobile phone users will be able to scroll around apps and websites using only their eyes, thanks to a new feature set to be unveiled by Samsung this week.

Samsung's hotly anticipated update to the Galaxy S3 will be unveiled on Wednesday 13 March in New York, and reports suggest the S4's top new feature will be eye control.

The S3, the only mobile to outsell the iPhone, already has a feature called Smart Stay that detects if users are looking at the screen.

The Smart Scroll feature on the new flagship Galaxy device will take this a step further.

A camera tracks the gaze, which in existing Galaxy phones is already used to stop the screen going dark while pages are being read, and to adjust the picture to the viewer's line of sight. Trademarks called "eye scroll" and "eye pause" were registered by Samsung in Europe in January, suggesting the new functions.

An image tweeted by the South Korean company invited fans to come to New York's Times Square, where the Galaxy S4 press conference will be streamed live on Wednesday, and samples of the smartphone will be available to try out afterwards.

A huge marketing and advertising campaign is expected to accompany the new phone. Samsung Electronics' marketing spend of £3.3 billion-a-year dwarfs that of many rival companies, including Apple, Microsoft, and bigger names such as Coca-Cola.

The battle between the top two heavyweight tech companies has been fierce, and since the release of the iPhone 5, Apple regained the number one slot.

But with the release of the Samsung Galaxy S4, many analysts believe the Samsung device will be the biggest seller when it hits the shops in a few weeks' time.

"Apple is not the one leading the market," said Francisco Jeronimo from analysis firm IDC. "I wouldn't be surprised if the new Samsung device sells more than the new Apple device over the next two years."

The latest model is understood to have a 5in display, 13 megapixel camera and even an eight-core processor - today's most advanced phones have four cores in their silicon chips. This means the S4 should have a bigger screen, take crisper pictures and process web pages faster than the iPhone 5, as well as a longer battery life.

Samsung has "enormous" plans for the handset, according to Peter Misek at Jefferies bank, with orders for 100 million in its first nine months. By comparison, Apple's bestselling phone to date, the 4S, took 15 months to ship 110 million units by the end of December.