Breaking up (banks) on Wall Street is hard to do

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The chorus of voices that wants to break up Citigroup grew Monday.

Keefe, Bruyette & Woods analysts became the latest to chime in and suggest the bank will need to keep unloading assets to keep investors happy.

"Citi's valuation remains near the lows since the financial crisis and we believe that is a reflection of investor views about the ultimate return of potential of the company post restructuring," KBW analysts wrote. "The primary motivation for splitting up would be the faster return of excess capital to shareholders."

Investors responded positively to the report, and Citigroup stock initially got a modest lift in early trading Monday before reversing to a decline.

However, it isn't clear whether Citi executives will take the push to unbundle the bank seriously, even after years of its stock trading beneath tangible book value, or the value of a company's equity minus assets that could not be sold in the event of liquidation.

"I don't think this is a good time to be doing deals," said Christopher Whalen, senior managing director at the Kroll Bond Rating Agency. "Why would you want to roll out a business now, with comps trading near a 52-week low?"