Google will launch a public test to show display and video ads on Google Video, another step in the search giant's slow exploration of graphical ads on its own services, according to sources familiar with the plans.

Possibly as early as Thursday or Friday, Google plans to announce it will stream for free some premium videos on Google Video which are normally fee-based, and accompany them with a banner-like ad and a video ad.

The banner-like ad will be displayed for the duration of the video on the Google Video player interface, while the video ad will be shown after the clip ends, sources said.

The ads and the videos will not be matched at random. Instead, advertisers will choose the videos they want to sponsor. In this manner, advertisers will avoid having their brand associated with a video they find objectionable.

The Google Video test may be short, running for only a week, and the ads will be attached to about 2,000 videos from about 8 providers. The videos will be from professionals, not amateurs. The test involves about 5 advertisers who are paying to participate.

After the test, Google is likely to continue revising and refining how it plans to display graphical and video ads on Google Video, sources said.

Google didn't respond to several calls seeking comment.

Google, whose revenue comes almost entirely from pay-per-click text ads, is under pressure to diversify its advertising mix and has indicated an intention to expand the scope of the ad formats it offers its advertisers. The company cited its interest in exploring display and multimedia ads as a reason for extending its partnership with AOL LLC at the end of last year.