Under fire for his role in the near-collapse of Citigroup Inc., Robert Rubin said its problems were due to the buckling financial system, not its own mistakes, and that his role was peripheral to the bank's main operations even though he was one of its highest-paid officials.

"Nobody was prepared for this," Mr. Rubin said in an interview. He cited former Federal Reserve Chairman Alan Greenspan as another example of someone whose reputation has been unfairly damaged by the crisis.

Mr....