WASHINGTON – Google Inc.’s Executive Chairman Eric Schmidt sparred with senators Wednesday during a hearing that repeatedly cast the Internet search leader as a greedy monopolist more driven to expand its empire than to steer Web surfers to the most helpful information.

Schmidt, Google’s chief emissary to the government, was put uncomfortably on the defensive as he trumpeted the company as a font of knowledge, innovation and economic opportunity during a 90-minute appearance before a Senate antitrust panel.

“Google does nothing to block access to any of the competitors and other sources of information” in Web searches, Schmidt testified. He acknowledged that Google is “in that area” of being a monopoly company but said it’s up to the courts to determine the question. The company recognizes that it has a special responsibility because of its market power, Schmidt said.

The political theater unfolded against the backdrop of a Federal Trade Commission investigation that threatens to handcuff Google as it tries to diversify beyond Internet search. Just last month, Mountain View, Calif.-based Google announced by far the biggest acquisition in its 13-year history – a proposed $12.5 billion deal to buy cellphone maker Motorola Mobility.

The FTC’s probe, triggered by rising complaints about perceived bias in the way Google ranks other websites, also is forcing the company to defend its pledge to make the world a better place. Google underscored that commitment by embracing “don’t be evil” as its corporate motto.

The biggest concern about Google is whether the company has been manipulating its results to prominently display its own services instead of rival websites. Those rankings can make or break websites because most people rely on Google to get around the Internet. Google processes about two-thirds of U.S. search requests and handles an even larger percentage in some parts of Europe.

The hearing by the Senate Judiciary subcommittee on antitrust turned up the heat on Google.

Sen. Michael Lee of Utah, the panel’s senior Republican, said “some of my fears have been confirmed” by Schmidt’s testimony.

Google appears to exploit its Web search dominance to reap an “unnatural and extraordinary advantage,” Lee said, adding that the company has a “clear and inherent conflict of interest” in its search results.

Sen. Richard Blumenthal, D-Conn., used a metaphor. “You run the racetrack, you own the racetrack,” he told Schmidt. Google now also owns some of the horses and “you seem to be winning,” Blumenthal said.

That prompted Sen. Al Franken, D-Minn., to wonder whether Google might also be “doping the horses.”