In a speech at Georgetown University's law school, Leibowitz said the agency was weighing evidence to decide if Google, the world's largest search engine, manipulated its search results to steer users to its new businesses, like travel search, which could be in violation of the law. Leibowitz later said that he expected a decision by the end of the year.

Google rivals specializing in travel, shopping and entertainment have accused Google of steering Internet users away from their websites to Google products that provide similar services. Google has repeatedly denied any wrongdoing.

"We are happy to explain our business to regulators and answer any questions they may have," Google spokesman Adam Kovacevich said in an emailed statement.

European regulators are conducting a similar antitrust probe.

(Reporting By Diane Bartz)

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