Days before the product ships in the US, Apple today announced that the iPhone will offer much more extensive battery life than first promised.

The shipping device will offer up to eight hours of talk time, six hours of internet use, seven hours of video playback or 24 hours of audio playback.

The iPhone will also provide up to 250 hours (over 10 full days) of standby time, the company revealed in its first statement on standby time.

Apple had originally promised battery life sufficient for up to five hours of talk time, internet use or video watching, and up to 16 hours of audio playback. (The page linked to here is the official iPhone specifications page, and is likely to be updated with new information soon).

Apple also confirmed another improvement - this time to the device's screen. "The entire top surface of iPhone, including its stunning 3.5-inch display, has been upgraded from plastic to optical-quality glass to achieve a superior level of scratch resistance and optical clarity," says the company.

Comments from Apple CEO Steve Jobs confirm the company's designs on the Smartphone market. "With eight hours of talk time, and 24 hours of audio playback, iPhone's battery life is longer than any other 'Smartphone' and even longer than most MP3 players," he said.

He added: "We've also upgraded iPhone's entire top surface from plastic to optical-quality glass for superior scratch resistance and clarity. There has never been a phone like iPhone, and we can't wait to get this truly magical product into the hands of customers starting just 11 days from today."

The device ships in the US on 29 June in a 4GB model for $499 and an 8GB model for $599. The device will be sold in the US through Apple's retail and online stores, and through AT&T's select retail stores.