CEO Steve Jobs opened Apple Inc.'s annual conference for software developers Monday by demonstrating the iPhone 4, which will cost $199 or $299 in the U.S. with a two-year AT&T contract, depending on the capacity. The iPhone 3GS, which debuted last year, will still be available, for $99.

The iPhone 4 is sleeker and more advanced than the original iPhone that came out in 2007. Like the iPhone 3GS, it comes in black or white, though it has a more angular look. Its front and back are covered with glass, and it is rimmed with stainless steel that acts as part of the phone's antenna.

It is about three-eighths of an inch thick; the iPhone 3GS is nearly half an inch. It can shoot high-definition video, catching up to some other smart phones. It has a gyroscope in addition to other sensors, to enable more advanced motion-sensing applications, such as games and mapping services.

The display on the iPhone remains 3.5 inches diagonally, but Jobs noted that it can show four times as many pixels — the individual colored dots that make up an image — as the previous screen. That makes for a sharper appearance.

One of the most noticeable changes is the iPhone's new camera on the front that can be used for videoconferencing, in addition to a five-megapixel camera and a flash on the back. For now, the videoconferencing function, FaceTime, works only if both parties to the call have an iPhone 4 and are connected over Wi-Fi rather than a cell phone network. Jobs indicated that FaceTime will eventually work over cellular networks, saying Apple needs to "work a little bit" with wireless providers to make it "ready for the future."

The battery on the new iPhone will allow up to seven hours of talk time — an improvement over five hours on the last model. It can handle up to six hours of Web browsing over cellular networks or 10 hours over Wi-Fi.

The new phone will run the latest version of Apple's mobile software, now called iOS4, which Apple unveiled in April to offer such features as the ability to operate more than one program at a time. Older iPhones and iPod Touch devices will be able to get iOS4 as a free download June 21, though not all features will work on them.

New applications for the device will include a version of the popular game Farmville and one from Netflix that lets people watch streaming video where they left off on their TV.

Apple is trying to tighten the links between the iPhone and its iPad tablet, which came out April 3. It is releasing a version of its iBooks e-reading application for the iPhone, which means people could buy an e-book from Apple on either device and read it on either one as well.