Jeffrey Greenberg, chairman and CEO of Marsh & McLennan Cos. Inc., New York, tendered his resignation to the firm's board of directors today, according to a source close to the situation. He is expected to be replaced by Michael Cherkasky, CEO of the firm's risk and insurance unit. Mr. Greenberg's resignation comes more than a week after New York Attorney General Eliot Spitzer accused Marsh & McLennan of bid rigging and conspiring with other insurers to fix prices; Mr. Spitzer had called for "changes in top management" but did not mention Mr. Greenberg by name. Marsh & McLennan is the parent firm of Mercer Investment Consulting and Putnam Investments. Barbara Perlmutter, Marsh & McLennan spokeswoman, did not return calls for comment.