Google Inc is confident that U.S. antitrust regulators will clear the search giant of any wrongdoing, Executive Chairman Eric Schmidt will tell a congressional panel on Wednesday.

Google has been broadly accused of using its clout in the search market to stomp rivals as it moves into related businesses, like travel search. The Federal Trade Commission is looking into that charge, and others, including that Google manipulates its search result rankings to favor its own products.

While no company would request such a government investigation, we are confident that our business practices will stand up to scrutiny, Schmidt said in written testimony submitted to the Senate Judiciary Committee's antitrust panel.

Representatives for rival companies, including Expedia Inc, Yelp Inc and Nextag Inc, will testify at the hearing after Schmidt.

Google controls more than two-thirds of the global search market. But Schmidt will argue specialty web sites -- like those with restaurant reviews and travel search -- give Google stiff competition.

Facebook is another competitor, Schmidt argues. Consumers, particularly young ones, increasingly are turning to their online friends to find out what to wear, where to eat, and what to watch, he said in written testimony.

Schmidt was Google's chief executive officer from 2001, but vacated the post to company co-founder Larry Page in April.

Schmidt now serves as executive chairman and oversees government affairs -- a position of critical importance during the FTC probe.

Schmidt has been defending Google in Washington for years and well knows that many antitrust experts are skeptical that Google always plays fair.

Key questioners are expected to be Democratic Senator Herb Kohl, head of the Senate Judiciary Committee's antitrust panel, and Democratic Senator Richard Blumenthal, who led investigations of Google when he was Connecticut's attorney general.

Republican Senator Mike Lee, also on the subcommittee, has expressed concern about Google's purchase of ITA travel search software.

Google could also be asked about a settlement with the Justice Department over Google accepting advertisements for prescription drugs that were illegally imported into the United States. Google paid $500 million in late August as part of a non-prosecution agreement.

Another witness at the hearing is Thomas Barnett, who was head of the Justice Department's antitrust division in 2008 when it stopped Google's attempt to pursue a joint venture with Yahoo.

Barnett, now representing online travel site Expedia, argued in his written testimony that Google uses its dominance of search to extend its power into areas like maps, product or travel search.

Google has been highly successful in many of these areas, often replacing the leading company (such as MapQuest) in an extraordinarily short period of time, Barnett said in his written testimony.

Yelp CEO Jeremy Stoppelman in his testimony criticized Google for using reviews from his web site, and others, to build Google's competing sites, Google Places.

Yelp provides user-generated reviews of restaurants, shops and other local businesses.

Stoppelman said Yelp objected to Google's use of its reviews, but was told Google would remove the reviews only if all of Yelp's content was made unsearchable -- making Yelp impossible to find on Google and a death sentence for any website.

Jeffrey Katz, the CEO of Nextag, an internet comparison shopping company, told lawmakers on Wednesday that Google was initially a huge help in building innovation in the Internet.

But what Google engineering giveth, Google marketing taketh away, said Katz in written testimony.

He argued that Google is now the Internet neighborhood bully.

Google doesn't play fair. Google rigs its results, biasing in favor of Google Shopping and against competitors like us, Katz said. As a result, Nextag's access is more and more discriminated against... because we compete with Google where it matters most, for very lucrative shopping users.

(Reporting by Diane Bartz; Editing by Tim Dobbyn)