At the World Economic Forum in January, Google's CEO, Eric Schmidt spoke of the company's intention to become one of the main players in the location-based mobile advertising market.

Now Google has opened a new revenue stream by selling ads to appear in web videos, which could include those on YouTube.

Google already sells adverts in text but now has signed up 20 companies to start targeting visitors through the web videos they watch, according to Reuters.

Partners include YuMe, an online video advertising network, Brightcove, an internet TV platform, and comedy site MyDamnChannel.

Brightcove's customers include CBS Corp, Time Warner and Discovery Communications.

YuMe is a new company based in California, and it told Reuters it is going to sell InVideo overlay adverts as part of Google's AdSense for video beta advertising programme.

Reuters adds that Google has been working on ways of developing advertising revenue for online video since it bought YouTube in November 2006.