A report from the Wall Street Journal this morning is the latest indication that U.S. antitrust regulators are gearing up for a possible antitrust battle with Google, focusing on whether the search giant has unfairly used its dominance in the Internet search business to favor its own products over those from its rivals.

The Federal Trade Commission is preparing to serve the company with civil subpoenas, starting “a wide-ranging, formal antitrust investigation” into the matter, according to the report. The investigation won’t necessarily lead to any charges, and any case that’s eventually brought would be difficult for the FTC to win, the report notes.

More than a decade ago, Microsoft was in a similar position as U.S. regulators investigated and ultimately filed suit over the company’s abuse of Windows’ market position.

Today, Microsoft is effectively Google’s largest competitor in the U.S. search business, thanks to the Redmond company’s alliance with Yahoo in search and advertising. Google holds about 65 percent of the U.S. search market, compared to a combined 30 percent for Microsoft and Yahoo, according to the latest numbers from the comScore research firm.

Microsoft in March filed an antitrust complaint against Google in Europe, where the search company has larger market share.

In a possible preview of elements of a U.S. case, that complaint alleged that Google that unfairly kept Microsoft Bing and Windows Phone from working properly with YouTube; attempted to gain exclusive access to many of the world’s books; prevented advertisers from porting their Google campaign data to Microsoft’s advertising system; blocked European web sites from using competing search boxes; and discriminated against rivals by “making it more costly for them to attain prominent placement for their advertisements.”

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