NEW YORK/WASHINGTON, May 15 (Reuters) - As talks over raising the U.S. government's $31.4 trillion debt ceiling intensify, Wall Street banks and asset managers have begun preparing for fallout from a potential default. Citigroup (C.N) CEO Jane Fraser said this debate on the debt ceiling is "more worrying" than previous ones. U.S. government bonds underpin the global financial system so it is difficult to fully gauge the damage a default would create, but executives expect massive volatility across equity, debt and other markets. Banks, brokers and trading platforms are prepping for disruption to the Treasury market, as well as broader volatility. Bond trading platform Tradeweb said it was in discussions with clients, industry groups, and other market participants about contingency plans.

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