Google Inc. co-founders Larry Page and Sergey Brin are slated for questioning by U.S. antitrust regulators and hired a top Washington law firm to help them prepare for their interviews, two people familiar with the matter said.

The Google executives retained Williams & Connolly LLP, the Washington law firm that has represented President Bill Clinton, former Federal Reserve Chairman Alan Greenspan and the late Senator Edward Kennedy, as counsel for the depositions, said the people, who didn’t want to be identified because they weren’t authorized to speak publicly about the matter. They didn’t know when the interviews are scheduled to take place.

Plans for the depositions come as the Federal Trade Commission speeds up its antitrust probe of operator of the world’s most popular Internet search engine. Jon Leibowitz, the agency’s chairman, said yesterday he expects to complete the investigation by the end of the year. The FTC will then decide whether to sue Google.

Google disclosed on June 24 that the FTC had begun a review of its business practices. The FTC is focusing on whether Google unfairly ranks search results to favor its own businesses and increases advertising rates for competitors, people familiar with the investigation have said.

Jill Hazelbaker, a spokeswoman for Mountain View, California-based Google, declined to comment on the hiring of counsel or the FTC’s planned depositions.

’We are happy to explain our business to regulators and answer any questions they may have,“ Hazelbaker said in an e- mail.

Peter Kaplan, an FTC spokesman declined to comment on the depositions. Lynda Schuler, a spokeswoman for Williams & Connolly, didn’t immediately return phone calls and e-mails after business hours seeking comment.

Google Chairman Eric Schmidt was scheduled to be deposed this week, a person familiar with the situation said May 30.

In April, the FTC hired Beth Wilkinson, a Washington litigator, to run the antitrust investigation, signaling that the agency may be building a case against Google.

Wilkinson, a partner with Paul, Weiss, Rifkind, Wharton & Garrison LLP, is working for the FTC two days a week while continuing to practice for the firm.

She wrapped up a case May 31 for video-game publisher Activision Blizzard Inc., which agreed to settle a lawsuit.