If John S. Reed's retirement pushes Citigroup Inc. into establishing a succession plan for the sole chief executive Sanford I. Weill, its main effect may be in establishing the identity of the unified financial conglomerate, some two years into its existence.

Mr. Reed, 61, on Monday announced his plans to retire on the date of the company's annual shareholder meeting, sparking immediate speculation on who might step into the job. Clouding the issue is that - as even Citigroup has acknowledged - the job's qualifications are still being defined.

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