In a notice posted on Google Mobile Blog, Christine Tsai, Product Marketing Manager, YouTube, said the company has started to display ads on select pages of the YouTube mobile site in the U.S. and Japan.

This test is considered to be the first step in the mobile advertising system for YouTube, as Google tries to find new ways to turn the video-sharing site to profits.

In June Google’s CEO, Eric Schmidt, said in an interview with the New Yorker’s writer Ken Auletta that the company plans to make some money out of YouTube, but it hasn’t figured out how to do so yet.

YouTube was purchased by Google for $1.6 billion, but so far, this money seems to have gone to charity, since the popular video site hasn’t managed to bring any profit to its parent company. On the other hand, the site has proven to eat out most of Google outgoing bandwidth.

Mr. Schmidt has said that the solutions for online advertising that will be implemented in the site will be made public next year. However it seems that ads that would run at the beginning of the videos that are posted on YouTube, a practice that has been adopted by other similar sites, is not an option that Google sees fit.

The two things that encourage Google in thinking that they will eventually be able to make YouTube profitable are the facts that there are plenty of people watching its clips and that the company has the luxury of taking its time in finding a solution.

The first ad system for YouTube was introduced last year, in August. The format enables a semitransparent ad to appear on a strip at the bottom of the video and it appears after a video plays for 15 seconds.

If the user who watches the video doesn’t click the ad it disappears up to 10 seconds later. The ad format is non-intrusive because the viewer can click to close the ad right away. In case he chooses to watch the ad, the main video pauses until the commercial stops.

However, Google didn’t release any details about the effectiveness  of its YouTube ad system.