Google executive chairman Eric Schmidt has been delegated to go and testify before the US Senate's antitrust subcommittee in September.
Google has been reluctant to send any of its managers but then the Senate reminded Google that it had subpoena powers.
Google had offered its chief legal officer David Drummond but the subcommittee wanted either Schmidt or new CEO Larry Page.
The Federal Trade Commission started a formal antitrust investigation of Google last month and the European Commission is already doing the same thing. The Justice Department is also investigating Google for illegally profiting from the sale of prescription drugs from online pharmacies and reviewing its recent $400 million acquisition of Admeld.