CUPERTINO, California (

TheStreet

) --

China Unicom

will start selling

Apple's

(AAPL) - Get Report

iPhone 4

in mid-September, according to a Chinese news report. The carrier will offer free cases in an attempt to prevent another

Antennagate.

The Chinese

Caixin Web site

, citing a China Unicom source, reports that the service provider will launch the new iPhone on Sep. 16, a move which is expected to shake up the country's smartphone market.

As the world's most populous nation, China presents a

great opportunity for smartphone makers such as Apple and HTC

, particularly at a time when the country is undergoing rapid economic growth.

China was the world's second-largest smartphone market during the second quarter of 2010, according to research from

Canalys

, and there is massive growth potential in a country of 1.3 billion people. Some 6.9 million smartphones were sold in China during the second quarter, although this number is expected to explode during the coming years.

Apple has already identified China as a major market opportunity. The company's Mac sales in China, for example, grew 144% during the third quarter, and Apple has also been ramping up its Chinese iPhone efforts.

China Unicom began selling an 8-Gbyte iPhone 3GS with Wi-Fi capabilities earlier this month. The telco, which is Apple's exclusive Chinese iPhone partner, has been

selling iPhones since late last year

although early versions of the iPhone had lacked Wi-Fi connections as a result of Chinese government regulations.

Apple, which posted

impressive third quarter results last month

, has described the iPhone 4 as its most successful launch ever, and has already sold more than 3 million of the new phones.

Analyst firm Gleacher & Company also believes that the

company's recent antenna problems

are already disappearing in the rear-view mirror, and predicts an imminent margin boost for the tech giant.

-- Reported by James Rogers in New York

Follow James Rogers on

Twitter.