Apple Inc. is preparing to introduce the next version of the iPhone on Sept. 12 in what will be a design overhaul of its top-selling product, according to two people with knowledge of the company’s plans.

The people asked not to be identified as an official announcement is yet to been made. The new iPhone will have a larger screen and thinner body, and is expected to work with faster long-term evolution wireless networks being introduced by carriers such as Verizon Wireless and AT&T Inc., according to analysts.

The design change will be Apple’s first for the bestselling smartphone since 2010, when it unveiled the iPhone 4. Last year’s update, the 4S, had the same look as the prior version. Anticipation for the new model has led to a drop in sales for the current devices, causing Apple to miss analysts’ sales and profit targets for three months that ended in June.

Apple is battling Samsung Electronics Co. for supremacy in the $219.1 billion smartphone market. While Apple’s strategy has been to release a single smartphone each year, Samsung has become the world’s leading handset maker by putting out several devices a year in a range of sizes and prices.

The planned September debut was reported earlier by iMore, a technology website. A spokesperson for Apple declined to comment.

The company increased the prepayments it is making for components by $1.15 billion – a jump that indicated a new product could be introduced, according to a report Monday from Maynard Um, an analyst at Wells Fargo Securities. Apple co-founder Steve Jobs had worked closely on the redesigned phone before his death in October, a person familiar with the matter said in May.