Google held its commanding lead as the preferred US search engine in May, processing almost 60 per cent of all queries filed, way ahead of its two closest competitors Yahoo and Microsoft.

Google nabbed 59.3 per cent of search queries, followed by Yahoo in a very distant second place with 22 per cent and Microsoft's MSN with 12.1 per cent, market researcher Hitwise said on Thursday.

Google's continued stranglehold on this market is significant considering that in recent years both Yahoo and Microsoft have invested heavily on developing and improving their search engine technology and accompanying search ad networks.

Microsoft and Yahoo officials strain to put on a happy face whenever they are confronted with Google's dominance. Both companies are fond of saying that search engine technology is still in its infancy and that consequently an opportunity exists to unseat Google as leader.

Still, when month after month trackers of search engine usage come out with their latest studies and Google remains firmly perched at the top, these predictions inevitably sound like wishful thinking and forced optimism.

Compared with March 2006, the May figures from Hitwise show Google gaining 1 percentage point of share, Yahoo staying almost flat and Microsoft losing 1 percentage point.

The search segment is the largest of the fast-growing US online ad market, accounting for 41 per ent of revenue, or about $5.1 billion. Online advertising spending grew 30 per cent in 2005 to US$12.5 billion.