Taking on Google’s Android mobile software in a key market, Apple said tonight it will launch the iPhone 4 in China on Sept. 25.

Apple said it will launch the hot-selling phone at Apple retail stores in China, including new stores in Shangai (pictured above) and Beijing. It will also be available the same day at China Unicom retail stores for buyers who want a two-year contract.

China is emerging as a key battleground in the smartphone wars. Apple’s advantage is its brand name as well as the 250,000 apps on its App Store. On top of that, the iPhone 4 has features such as its FaceTime video phone, a high-definition Retina display, high-definition video recording, and a 5-megapixel camera.

Apple will sell the device for CNY 4,999 for the 16 gigabyte model and CNY 5,999 for the 32-gigabyte model without a contract. It will be an interesting battle, since China has been a stronghold for Android. The Android phones have been lower cost, which is appealing in China. On the other hand, those who aspire to be cool in China — part of a growing middle class there — will likely embrace the coolness associated with the iPhone brand.