The Federal Reserve is preparing a proposal to raise the asset-based thresholds that determine how stringently big U.S. banks are supervised-a plan that could come by year's end, Reuters reported on Friday.

Such a plan was expected by industry analysts and bankers whose lobbyists have long urged regulators to rework the levels that trigger stricter oversight of large lenders.

A spokesperson for the Fed declined to comment to Reuters, which cited anonymous sources.

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