Apple Inc. on Wednesday unveiled the latest version of its wildly popular iPhone, as it steps up efforts to increase its share of the lucrative global smarthphone market amid stiff competition from Google's Android-powered devices.

iPhone 5 is thinner, lighter, bigger and faster than its predecessor.

The new iPhone is 18% thinner and 20% lighter than the iPhone 4S. Apple claims it is the thinnest smartphone in the world.

iPhone 5 has a four-inch screen compared to the 3.5-inch screen that the previous versions of the device sported.

The iPhone 5's processor speed is twice as fast as the previous version, according to Apple. 

It is also the first iPhone to have 4G-LTE network connectivity, which allows for speeds of up to 10 times faster than 3G.

In the United States, the iPhone 5 will be compatible with the LTE networks supported by Verizon, AT&T and Sprint.

The iPhone 5 will go on sale on Sept. 21, starting at $199 for the 16-gigabyte version with a new two-year contract. Larger 32 GB and 64 GB versions will cost $299 and $399, respectively. 

Apple will begin taking pre-orders on Sept. 14.

The two previous versions of the iPhone will continue to be sold at reduced prices. The 16 GB iPhone 4S will get a US$100 price cut, selling for US$99, and the iPhone 4 will be free with a two-year contract.

The updated iOS 6, the iPhone's new software, will be available for download on most older versions of the iPhone on Sept. 19.

Wall Street analysts expect Apple to sell 45mn iPhone 5 units in the first three months after it hits stores. Apple sold 37mn units of iPhone 4S in the first quarter after it went on sale last fall.