"American antitrust law is designed to promote innovation and help consumers, not tilt the playing field in favor of particular competitors or make it harder for people to get the services they want," Google senior vice president Kent Walker said in a blog post on Tuesday.
The lawsuit by the Justice Department and 11 states alleges Google used its market power to fend off rivals, including through distribution agreements that gave its search engine prominent placement on phones and internet browsers.
Google says those agreements, in which it shares revenue from search ads with distributors such as iPhone maker Apple Inc, help subsidize phones.
Companies could carry other search engines, but users have repeatedly shown a preference for Google's search tools, Walker said. Consumers who prefer an alternative are able to switch the default search tool on iPhones and other devices, he said. But forcing device and browser makers to set "lower-quality search alternatives" as the default was not beneficial to consumers, Walker added.
He also described as incorrect the Justice Department's conclusion that topic-specific search tools such as travel services Kayak and Expedia or shopping giant Amazon.com Inc were not competitors to Google search.
Google contends the popularity of those narrow search tools lowers its market share than when counting only Microsoft Corp's Bing and other "general" search tools as competition.
(Reporting by Paresh Dave; editing by Edward Tobin)
By Paresh Dave