YouTube, the world's largest video-sharing service, on Tuesday launched a new official application with advertising for Apple's iPhone, one day before Apple is set to unveil the latest generation of its smartphone.

YouTube, the world's largest video-sharing service, on Tuesday launched a new official application with advertising for Apple's iPhone, one day before Apple is set to unveil the latest generation of its smartphone.[File photo]

According to YouTube's official blog, users of iPhone and Apple 's iPod Touch media player can download the YouTube app starting from Tuesday. The app works on Apple's iPad tablet, but currently is not optimized for the bigger screen. YouTube said an optimized iPad version will be available in the coming months.

The new app offers more videos and features than the current pre-loaded version on Apple devices. By showing ads, the app will enable users of devices running on Apple's iOS software to watch some of the most popular videos as major labels and big publishers had opted out the previous ad-free YouTube iOS app.

The app also provides more search and sharing features, like swiping to view the channel guide and easier sharing through social networks such as Twitter, Facebook and Google+.

Behind the new app is the increasingly strained relationship between Apple and YouTube's mother company Google, as Apple has been slowly stripping off Google's influence in its mobile system.

Besides search, Google once had several products integrated into Apple's iOS system, like Google Maps and YouTube. In June, Apple announced its own mapping service on iOS, expanding from the current features of Google Maps.

Apple has been pre-installing YouTube on iPhones since it launched the first generation of the popular smartphone in 2007. In August, Apple said its latest mobile system iOS 6 will be no longer pre-loaded with YouTube.

According to YouTube's blog, the video service now has 1 billion mobile views a day, accounting for one quarter of its daily views.

As Apple's long-expected iPhone 5 will be unveiled with iOS 6 on Wednesday, Google's challenge is to convince people to download the YouTube app on iOS devices and maintain the number of its mobile views, some analysts said.