With anticipation at a fever pitch, Apple CEO Steve Jobs unveiled the iPhone 3G to an appreciative audience during the opening keynote speech at the company's Worldwide Developers Conference.on Monday.

The new iPhone, sporting a thinner and sleeker look, will support faster 3G (third-generation) broadband wireless networks and come with built-in GPS (Global Positioning System) capabilities, Jobs said. Support for 3G networks will enable the new iPhone to download data up to 2.8 times faster than the earlier model, Jobs said. Built-in GPS will make it easier for users to navigate roads.

The iPhone 3G will come with a 3.5-inch screen and have better battery life, with talk time of five hours, stand-by time of 300 hours, six hours of high-speed browsing time, 20 hours of audio and seven hours of video, Jobs said. Some who had previously bought iPhones complained about its battery life and that was a problem that Apple needed to solve with the new iPhone, Jobs said.

Quicker data downloads and lower prices are key to greater adoption of iPhones worldwide, Jobs said. Apple has cut the price by half to make the new iPhone more affordable for users, so that the 8G-byte model will sell for US$199 and the 16G-byte model for $299. The company found that 56 percent of people surveyed wouldn't buy the earlier iPhone because they found it expensive.

The phone will ship on July 11 in North America and will eventually be rolled out in 70 countries, including India, China, Singapore and Australia, Jobs said.

The release ends months of speculation surrounding the iPhone 3G's release date and features. Apple earlier acknowledged that stocks of the original iPhone were low in the U.S. and Europe, fueling speculation that Apple was winding down supplies to ready the market for iPhone 3G.

In the U.S., AT&T is ready for the new iPhone, announcing last week that it had upgraded its 3G wireless network with improved downlink speeds of up to 1.7M bps (bits per second), a 20 percent increase over previous speeds. The broadband network is available in many U.S. metropolitan areas and the carrier intends to expand it. The network uses HSDPA (High Speed Downlink Packet Access) technology.

Jobs also said Apple will preview the new version of Mac OS X, code-named "Snow Leopard," an upgrade to Leopard, the current version of Mac OS X, during the show. He provided no further details about the features or release date, focusing instead on the new iPhone. He also officially announced iPhone 2.0, a new software platform for the smartphone. Stressing the use of the iPhone as an enterprise device, Jobs said the new platform will build in support for Microsoft Exchange, allowing enterprises to push e-mail, contacts and calendars from Exchange server to the iPhone.