SEATTLE — Microsoft Corp., the No. 3 Web search provider in the U.S., is rolling out changes to its search engine aimed at narrowing the gap between it and market leader Google Inc.

Microsoft is quadrupling the number of sites it searches for new information and overhauled the core technology that decides which results to display, said Satya Nadella, a Microsoft corporate vice president.

Nadella said the updates will be phased in by the end of the month. Among them, he said, are improvements in the way Live Search interprets what users are looking for, even if they misspell a word, type in two separate words instead of a compound word or use a variation, like "driving" instead of "drive."

In August, Microsoft snagged 11 percent of U.S. Web searches, far behind Google Inc.'s 57 percent and Yahoo Inc.'s 23 percent. Making money from search depends on volume, and Microsoft has its eye on the billions of dollars Google rakes in from search-related keyword advertising.