Yahoo will be serving up graphical ads to mobile phones as part of a test to extend corporate brand marketing from the internet to mobile phones.

Yahoo on Monday said it would begin a public test of banner-like ads this week with users of the Yahoo Mobile Web service in the U.S., writes Reuters. Users can click on interactive ads to see more details of an offer or to call the advertiser. The ads measure 150 x 21 pixels, taking up a small portion at the top of the screen. The brand advertising test comes a month after Yahoo's U.S. and U.K. test to deliver text ads tied to searches performed on mobile web browsers.

Yahoo Mobile Web is available on most phones offered by major U.S. wireless operators and offers access to Yahoo search, email, news, stock quotes and sports.

As more users buy newer phones sign up for high-speed mobile internet services, eventually "consumers will treat the phone as a mini-web experience," according to a Jupiter analyst quoted by Reuters. "Now is the time for Yahoo to experiment."