MOUNTAIN VIEW, Calif. — The new Web browser that Google Inc. released yesterday is designed to expand its huge lead in the Internet search market and reduce Microsoft Corp.'s imprint on personal computers.

The free browser, called "Chrome," is being promoted as a sleeker, faster, safer and reliable alternative to Microsoft's Internet Explorer, which has been the leading vehicle for surfing the Web for the past decade. Despite recent inroads by Mozilla Foundation's Firefox, Internet Explorer is still used by roughly three-fourths of the world's Web surfers.

"What we want is a diverse and vibrant ecosystem," Google co-founder Sergey Brin told reporters yesterday during Chrome's unveiling. "We want several browsers that are viable and substantial choices."

Among other features, Chrome's navigation bar — the space where you type in an Internet address — will serve a dual purpose. Users can either enter an address into the space or type a search request that will be processed through their search engine of choice.

Naturally, Google bets it will be the default search engine for the majority of Chrome users, helping to build upon its nearly 64 percent share of the worldwide search market.

"You only have 24 hours a day and we would like you to do more searches," Google's other co-founder, Larry Page, said at the unveiling. "If the browser runs well, then you will do more searches."

And more queries generate more revenue for Google, whose search engine is the hub of the Internet's largest advertising network.

Google also is counting on Chrome to become the linchpin in its effort to distribute widely used computer programs like word processing, spreadsheets and calendars through the Web browser instead of as applications installed on individual machines. If the crusade is successful, it might undercut Microsoft's profits by diminishing sales of its Office software package.

"Chrome will strengthen the Web as the biggest application platform in the world," predicted Jon von Tetzchner, chief executive of the company that makes the Opera browser, which ranks a distant fourth in the market.

Microsoft, which crushed Netscape Communications to win the last major browser war in the 1990s, played down the threat posed by Chrome. The Redmond, Wash.-based software maker predicted that most people will embrace its latest version, Internet Explorer 8, which it released in test status last week.

"IE8 is designed to put users in control of how and where they navigate, improve their day-to-day browsing, keep people safe from real threats ... and respect people's privacy online," Dean Hachamovitch, Internet Explorer's general manager, said in a statement yesterday.

But Benchmark Co. analyst Brent Williams thinks Microsoft has cause for concern. In a research note yesterday, Williams described Chrome as a "a new, potentially significant, challenge to Microsoft's Web strategy and to (Microsoft's) core product suite, and indeed to (Microsoft's) business model."

Microsoft shares fell 19 cents to $27.10 Tuesday while Google shares gained $1.96 to $465.25.