Apple’s next-generation iPhone will have a faster processor and will start shipping in September, several sources with direct knowledge of the company’s supply chain said.

The production of the new iPhone will start in July/August and the smartphone will look very similar to the current iPhone 4, one of the sources said on Wednesday.

The iPhone -debuted in 2007 with the touchscreen, on-demand application template now adopted by its rivals- remains the gold standard in the booming smartphone market.

Reports on the timeline of the new iPhone launch vary, though it is largely expected that Apple will likely refresh its iPhone 4 later this year.

The sources declined to be identified because the plans for the new iPhone were not yet public. An Apple spokeswoman in Hong Kong was not available for comment.

The iPhone is one of Apple’s most successful products, with more than 16 million sold in the last quarter of 2010 and the product accounted for more than a third of the company’s sales in the quarter.

The current iPhone 4 was launched by Apple Chief Executive Steve Jobs in June last year and began shipping the same month in 2010.

Apple sources many of its components from Taiwan-based suppliers, many of whom are expected to benefit from an uptick in sales as some of them rely on the U.S. company for about 20-40 percent of their business, said Vincent Chen, an analyst at Yuanta Securities.

Apple, a big purchaser of touchscreen displays and flash memory, is also dependent on Japan for some of its key components, sparking concern that the disruption due to the crisis there may hurt its gross margins.

Apple is expected to report another spectacular quarter on Wednesday, tempered by growing caution over how supply constraints will squeeze margins and restrain iPhone and iPad sales.