American International Group (AIG) Chairman Harvey Golub has resigned following the breakdown of his relationship with AIG CEO Robert Benmosche.

Mr Golub’s resignation last week was effective immediately. He has been replaced by AIG director and former Delphi Corporation CEO Robert (Steve) Miller.

In his resignation letter, Mr Golub said Mr Benmosche has informed the AIG board that their working relationship was “ineffective and unsustainable”.

“Asking the board to choose between us would be an abdication of my responsibility to lead,” he said. “Consequently, I’m resigning for the simple reason I believe it is easier to replace a chairman than a CEO.”

Mr Golub, a former CEO of American Express, became AIG’s fifth chairman since 2005 in August last year.

The breakdown of relations between the two men is said to have resulted from the failed sale of the company’s Asian unit AIA Group to Prudential.