Harvey Golub says he is stepping down as chairman of American International Group Inc. so that Robert Benmosche will continue to be the company’s chief executive officer.

Golub, who became chairman of AIG, New York (NYSE:AIG), in August 2009, has written in a letter to George Miles, chairman of the AIG governance committee, that he is resigning from his position as an AIG director as well as the company’s chairman.

Benmosche, a former chairman of MetLife Inc., New York (NYSE:MET), who has been the AIG CEO since August 2009, “has informed the board that he believes our working relationship as chairman and CEO to be ineffective and unsustainable,” Golub writes in the letter, which as published by AIG in a press release distributed through Business Wire.

“At this point, I view asking the board to choose between us would be an abdication of my responsibility to lead,” Golub says. “Consequently, I’m resigning for the simple reason I believe it is easier to replace a chairman than a CEO – particularly a company in the midst of two major activities: (1) a major corporate restructuring, and (2) development of an exit plan from government control, both of which involve executing a long list of difficult tasks.”

Fellow directors have expressed their desire for Golub to continue to be chairman, Golub says.

“I’m proud of all of you and the work we have accomplished in moving AIG from a company being dissolved to one on the cusp of having an implementable strategy to pay back the government and stand on its own as a viable and independent insurance company,” Golub says. “I wish all of you the best of luck. It has been my privilege to work with you.”

Golub was chairman and CEO of American Express Company, New York, from 1993 to 2001.

Steve Miller, 68, the new AIG chairman, is a turnaround management specialist who has been on the AIG board since June 2009. He was chief financial officer of Chrysler Corp., Detroit, in the mid-1990s, and later was chairman of companies such as Bethlehem Steel and Delphi Corp. He is now chairman of MidOcean Partners, New York, a private equity firm. He has a bachelor’s degree and a master’s degree in business from Stanford University and a law degree from Harvard University.

“AIG has established strong momentum over the last year, and we remain fully committed to delivering on AIG’s core priorities: Repaying taxpayers, meeting all of the company’s obligations to its various stakeholders, and restructuring the company so that it emerges as a smaller, more focused enterprise worthy of investor confidence,” Miller says in a statement about the transition.