Microsoft increased its share of the U.S. Internet search market by another 1 percentage point in July, taking its combined share with new search partner Yahoo to 20.36 percent, according to data released on Monday.
Internet data firm StatCounter said Microsoft's new Bing search engine had 9.41 percent of the U.S. market in July, up from 8.23 percent in June. Google's share slipped to 77.54 percent from 78.48 percent.
Microsoft and Yahoo announced a 10-year Web search deal last week to challenge Google.
They plan to use Bing to power search queries on Yahoo's sites, with Yahoo's sales force taking responsibility for selling premium search ads to big buyers for both companies.
StatCounter said on Monday: Bing continues to make slow but steady progress but the combined Yahoo figures suggest that the deal announced last week will have to demonstrate major future synergies if it is to make any dent in Google's dominance.
StatCounter said Google's share of the global search market slipped in July to 89.23 percent from 89.80 percent in June.