Google executive chairman Eric Schmidt has agreed to testify at a US Senate hearing into online competition in September.

Google had initially been reluctant to send Schmidt or chief executive Larry Page to the hearing of the Senate Subcommittee on Antitrust, Competition Policy and Consumer Rights.

But subcommittee chairman Herb Kohl, a Democrat from Wisconsin, said Friday that the Internet search giant had agreed to send Schmidt, who stepped down as CEO in April to become executive chairman.

"We look forward to Eric Schmidt's participation at our Antitrust Subcommittee hearing in September," Kohl said in a statement. "This will allow us to have a truly informational and thorough public hearing."

Kohl and Senator Michael Lee of Utah wrote to Google last month asking that Page or Schmidt attend the hearing on competition issues in Internet search.

Google proposed that chief legal officer David Drummond testify instead but the two senators said they would "strongly prefer" that Page or Schmidt attend the hearing.

US regulators last month launched a probe into Google's lucrative search and advertising business in a move that could pose the most serious legal challenge yet to the Internet titan.

The Mountain View, California-based company controls around 65 percent of the Internet search market in the United States and earns billions from search-related advertising.