SAN FRANCISCO - YAHOO Inc has spent almost four years trying to catch up to Google Inc in Web search technology. On Tuesday, it's trying to jump ahead.

Yahoo plans to unveil a revamped search engine that it says delivers faster, more relevant and engaging results than market leader Google, which conducts more than half of the Web's search requests.

Sunnyvale-based Yahoo said the upgrade was the most significant yet since it dumped Google's search technology in February 2004 in favour of its own.

Yahoo, the No. 2 search engine, has fallen further behind Google in market share despite its improved technology. Web users chose Google for 57 per cent of their searches in August, compared with 23 per cent for Yahoo.

The challenge facing search engines: Getting Internet searchers to break the Google habit. 'Yahoo is fighting an uphill battle,' said Scott Kessler, an analyst with Standard & Poor's. 'Google has become so inextricably connected with the concept and practice of search, Yahoo has to work a lot harder to get on people's radar screens.'

Yahoo is starting by trying to change the search habits of the hundreds of millions of people who visit its stable of Web sites. Gaining market share is critical as Yahoo starts to see results from Project Panama, the ad-placing technology that is expected to help the company generate more profit from each search conducted.

'One of the things we are looking for is to give people a reason to come to Yahoo to try search,' said Tim Mayer, vice president of product for Yahoo Search. 'This is very visible. It shows we are serious about search, that we are making some gains in market share and that we are providing users with a better experience.'

Forrester Research analyst Charlene Li said Yahoo's improvements were significant. 'Yahoo is taking search to a different level primarily because they are doing what I call 'mind readin' - anticipating what you are going to do,' she said.

For example, when users type search terms, Yahoo will show suggestions for more refined ways to search for the information.

Yahoo is the latest search player to overhaul the way its presents search results in an effort to chip away at Google's lead. Ask.com, owned by IAC/InterActiveCorp, relaunched in June with a dramatically different looking interface, and Microsoft Corp last week showed off its new method for displaying search results.

Doug Leeds, vice president of product management for Oakland-based Ask.com, dismissed the Yahoo changes as 'catch-up'.

To deliver a better experience, technologists pore over behavioral patterns and complex algorithms to find new ways to help people more quickly and easily find the information they are seeking. Much of that innovation centers on understanding user intent - when they type 'apple' are they seeking fruit or computers?

New Yahoo features include suggesting different ways to phrase a search request, offering a list of related concepts, generating more links to photos, videos and music and making it easier to find local information as well as information about popular pursuits such as sports, entertainment and health.

To gain traction in the search business, Yahoo must increase traffic and advertiser interest, analysts say. It also must get users to click more often on search ads by making them more relevant to what they're looking for - an area in which Google has excelled. 'One search at a time, that's how you win this battle,' Li said. -- AP