The new YouTube app will be available for download at Apple's App Store beginning on Tuesday, Google said in a blog on the company website on Tuesday.

Web-connected smartphones are increasingly important to YouTube's business. One billion of YouTube's daily video views now occur on mobile devices, said Google. Earlier this year YouTube said it was streaming 4 billion videos every day.

The new YouTube app for the iPhone will feature thousands of additional videos, according to the blog post, as well as improved features for finding videos and sharing videos on social networks.

Unlike the previous version of the YouTube iPhone app, the new version will feature online advertising, a Google spokesman said.

Online ads generate the bulk of Google's revenue, the world's No.1 Web search engine, and YouTube already offers ads on its mobile website and on the version of the app for Android smartphones.

Apple said last month that its license to include the YouTube app in the iOS operating system used by the iPhone and iPad had ended.

The relationship between Google and Apple has frayed over the years, as the shift from PCs to mobile devices has increased the competition between the two companies. Earlier this year, Apple said it would dump Google's mapping software from its mobile devices.

Apple is holding a press event in San Francisco on Wednesday where many expect the company to unveil a new version of its iPhone.

YouTube has been among a handful of apps that came pre-loaded onto the screens of Apple's mobile devices since the original iPhone was introduced in 2007.

The pre-installed YouTube app -- which was actually built by Apple using YouTube standards -- was not as full-featured as YouTube's own website, but it was popular.

According to data measurement firm Nielsen, YouTube was the third most popular iPhone app by users, including both pre-installed apps and downloaded apps, in the U.S. in June.

Google said it was working on a version of the YouTube app specially-designed for iPads, which should be available in the coming months.

(Reporting By Alexei Oreskovic; Editing by Michael Perry)

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