Google is calling its concept 'knol' - the California-based company's shorthand for a 'unit of knowledge' - and it will consist of material submitted by people who want to be identified as experts and possibly profit from their knowledge.

For now, submissions are by invitation only, but the Internet search leader said it will eventually publish articles by all comers.

The concept poses a potential challenge to the non-profit Wikipedia, which has drawn upon the collective wisdom of unpaid, anonymous contributors to emerge as a widely used reference tool.

'There are millions of people who possess useful knowledge that they would love to share, and there are billions of people who can benefit from it,' Mr Ubi Manber, Google's vice-president of engineering, wrote in the company's posting about the new service. 'We believe that many do not share that knowledge today simply because it is not easy enough to do that.'

Since it was founded on the same knowledge-sharing premise six years ago, Wikipedia has compiled 2.1 million English-language articles as well as millions more in dozens of other languages.

Wikipedia attracted 56.1 million US visitors in October, making it the eighth most popular website, according to comScore Media Metrix.

In a Friday interview, Wikipedia founder Jimmy Wales downplayed Google's latest move. 'Google does a lot of cool stuff, but a lot of that cool stuff doesn't work out so great,' he said.

The Googlepedia, as some observers are calling the new offering, will identify who wrote each article - Wikipedia's cloak of anonymity has been criticised as an opportunity for abuse.

But Google will not 'serve as an editor in any way, and will not bless any content', Mr Manber wrote, letting visitors rate the entries and leave comments.

Mr Larry Sanger, editor-inchief of Citizendium, another Web-based encyclopaedia that has editors, said this opens 'knol' to 'precisely the same sort of uneven content, with many of the same abuses, that Wikipedia has'.

Google also wants to make money off its encyclopaedia.

Although the resource will be available for free, the company wants to place ads related to the topics covered on each page.

AP