Back in January when Steve Jobs introduced its latest gadget, iPhone, critics rushed to point out a possible disadvantage: the battery life. Speaking about the features of iPhone at WWDC, Steve Jobs said that iPhone will 5 hours of video/talk time and 16 hours of audio playback.

But today, with the iPhone launch coming just few days away, Apple decided to reveal a secret. According to a press release issued by the Cupertino company iPhone will deliver longer battery life when it ships on June 29 than was originally estimated when iPhone was unveiled in January.

The new iPhone (although is rather strange to refer to a product as “new” when it is days away from official premiere) will feature up to 8 hours of talk time, 6 hours of Internet use, 7 hours of video playback or 24 hours of audio playback. The standby estimated by Apple is 250 hours - more than 10 days.

Other big news is that Apple, inspired probably by previous incidents with iPod nano, upgraded the entire top surface of iPhone, including its 3.5-inch display, from plastic to optical-quality glass to achieve a superior level of scratch resistance and optical clarity.

“With 8 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,” said Steve Jobs, Apple’s CEO.

“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 upgraded iPhone may be considered as Apple’s response to the touch-screen mobile phones launched in the past months by Samsung, LG, HTC or Sony Ericsson.