A US Senate Judiciary subcommittee will holding a hearing today on the Google and Yahoo search advertising deal.

The hearing before the Subcommittee on Antitrust, Competition Policy and Consumer Rights on 'The Google-Yahoo Agreement and the Future of Internet Advertising' comes as the US Department of Justice continues its antitrust investigation into the advertising partnership.

On June 12, Yahoo said it would run advertisements supplied by Google alongside search query results, a four-year deal estimated to bring Yahoo up to $800m in revenue a year.

The witnesses scheduled to testify at the hearing are: David Drummond, Google's senior vice president, corporate development and chief legal officer; Michael Callahan, Yahoo's general counsel; Brad Smith, Microsoft's senior vice president and general counsel; Matthew Crowley, chief marketing officer, Yellowpages.com in California, and Tim Carter, president and CEO, Askthebuilder.com, and a US newspaper columnist.